2025-12-17 REL PDBe INITIAL_RELEASE REPOSITORY INITIAL_RELEASE REPOSITORY INITIAL_RELEASE REPOSITORY EXPERIMENTAL_SUMMARY em_admin _em_admin.last_update DERIVED_CALCULATIONS em_imaging_optics em_software struct_conn _em_imaging_optics.energyfilter_name _em_software.name REFINEMENT_DESCRIPTION refine refine_hist refine_ls_restr refine_ls_shell _refine.pdbx_refine_id _refine_hist.pdbx_refine_id _refine_ls_restr.pdbx_refine_id _refine_ls_shell.pdbx_refine_id DERIVED_CALCULATIONS pdbx_validate_close_contact struct_conn struct_conn_type OTHER atom_sites cell _atom_sites.fract_transf_matrix[1][1] _atom_sites.fract_transf_matrix[2][1] _atom_sites.fract_transf_matrix[2][2] _atom_sites.fract_transf_matrix[3][2] _atom_sites.fract_transf_matrix[3][3] _cell.Z_PDB STRUCTURE_SUMMARY chem_comp_atom chem_comp_bond database_2 em_admin pdbx_entry_details pdbx_modification_feature struct_conn _database_2.pdbx_DOI _database_2.pdbx_database_accession _em_admin.last_update _struct_conn.pdbx_dist_value _struct_conn.ptnr1_auth_asym_id _struct_conn.ptnr1_auth_comp_id _struct_conn.ptnr1_auth_seq_id _struct_conn.ptnr1_label_asym_id _struct_conn.ptnr1_label_atom_id _struct_conn.ptnr1_label_comp_id _struct_conn.ptnr1_label_seq_id _struct_conn.ptnr2_auth_asym_id _struct_conn.ptnr2_auth_comp_id _struct_conn.ptnr2_auth_seq_id _struct_conn.ptnr2_label_asym_id _struct_conn.ptnr2_label_atom_id _struct_conn.ptnr2_label_comp_id _struct_conn.ptnr2_label_seq_id DATA_COLLECTION em_admin _em_admin.last_update PDBe PDBe 2016-07-17 2016-08-03 2016-08-03 2025-12-17 Galej WP Wilkinson MF spliceosome, snRNP, pre-mRNA splicing, trans-esterification, lariat intermediate, complex C, splicing Galej WP Wilkinson ME Fica SM Oubridge C Newman AJ Nagai K Nature UK 537 197 201 2016 27459055 doi:10.1038/nature19316 1476-4687 0006 NATUAS 5lj3 unknown EMDB EMD-4055 associated EM volume Spliceosome immediately after branching Spliceosome immediately after branching 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31

Splicing extract was prepared from Prp18-HA or Slu7-TAPS yeast strains. An in vitro transcribed yeast UBC4 pre-mRNA substrate (with 2 x MS2 bacteriophage coat protein-binding stem loops at the 5' end and with the 3'-splice site sequence UAGAG mutated to UACAC) was pre-bound to an MS2-maltose binding protein fusion protein. This substrate-protein complex was added to the splicing extract. The splicing reaction proceeded through the first step but the second step was blocked by the 3' splice site mutation. Substrate-bound spliceosomes from the splicing extract were purified on amylose resin and eluted with maltose. Subsequently the spliceosomes were captured on anti-HA-agarose (for Prp18-HA-tagged) or streptactin resin (for Slu7-TAPS tagged) and eluted with HA peptide or desthiobiotin, respectively. Purified spliceosomes were then dialysed against 20 mM HEPES KOH pH 7.8, 75 mM KCl, 0.25 mM EDTA

Saccharomyces cerevisiae 2 U5 snRNA (small nuclear RNA) Saccharomyces cerevisiae 0.057444875 1 AAGCAGCUUUACAGAUCAAUGGCGGAGGGAGGUCAACAUCAAGAACUGUGGGCCUUUUAUUGCCUAUAGAACUUAUAACG AACAUGGUUCUUGCCUUUUACCAGAACCAUCCGGGUGUUGUCUCCAUAGAAACAGGUAAAGCUGUCCGUUACUGUGGGCU UGCCAUAUUUUUUGGAACU CP007851.1 Exon 1 (5' exon) of UBC4 pre-mRNA Saccharomyces cerevisiae 0.005170152

This RNA was produced from an in vitro transcribed yeast UBC4 pre-mRNA with two stem-loops added at the 5' end for binding by the MS2 bacteriophage coat protein. This pre-mRNA is added to a yeast splicing extract and the first step of splicing yields the 5' exon and the lariat intron-3' exon intermediate, which both remain associated with the spliceosome.

1 UAAGUGAUCUAGAAAG Intron of UBC4 pre-mRNA Saccharomyces cerevisiae 0.024109115

This RNA was produced from an in vitro transcribed yeast UBC4 pre-mRNA with two stem-loops added at the 5' end for binding by the MS2 bacteriophage coat protein. This pre-mRNA is added to a yeast splicing extract and the first step of splicing yields the 5' exon and the lariat intron-3' exon intermediate (this RNA), which both remain associated with the spliceosome.

1 GUAUGUCUAAAGUUAUGGCCACGUUUCAAAUGCGUGCUUUUUUUUUAAAACUUAUGCUCUUAUUUACUAACAAAAU X17493.1 U2 snRNA (small nuclear RNA) Saccharomyces cerevisiae 0.376267406 1 ACGAAUCUCUUUGCCUUUUGGCUUAGAUCAAGUGUAGUAUCUGUUCUUUUCAGUGUAACAACUGAAAUGACCUCAAUGAG GCUCAUUACCUUUUAAUUUGUUACAAUACACAUUUUUUGGCACCCAAAAUAAUAAAAUGGACGGGAAGAGACUUUUUAAG CAAGUUGUUUUCCGCUAAUGUCAGGUCUCACUACUUUUUGCUGCUAUUUUUCUUCGCUCAUGGUUUCUUCAUAAGGCGUU UUUAUGAUGGUUUUUCGAAAUUGGUUUUUGAGACGACGGUUGCUCAAGGUUAUUGUUUUUGUUUUCUUCUGGUUGUUUUC UAUUUUCUUUUUUUUAGCUUUCUGUUUCUCCCUUAGUUUGGCUUUUUGCUUCAUACUCUUCCCUGUCUUUCCGAGCCGUU UAUGUCCAACGCGGGAUUUGGUUUUUCUUUAUCGAUGGGAAGAAAUGGUGCUAUAGUAGGUUGGGAGAUAAUAUUUAUGG UAUGGGGUGCUAGUGCGGAUGGGGCGCUCUUAUUGUUGAUUUCUUCGCUCGUCUUCUUUUUCUGGUGGCGCUGCAAGAGG AAGUUUUUCGACUUUGUUAUGAUUUUUGGUUUGCAAGGAAAGGUGUCUUACGAUUCUUUUUUUGAUGUAAUAGGAUAAGC UUGCUUAUCCCCCAAGUAUCGGCCAAAGUUGUUGAUUUUCCUUUUGAAGUGUCCUCGGUUUGAGGGGGUGUAGGGUGGGG UUGGUCUACAAUAAGAGUGUUCCAUUGUUAACGUGCUGGCGUCUUUUACUAUAUUUUUUUUCCCAGUUUAUUUUGUGCUU AUUUUCUCAUUGAGGAGAAGGAGCUCUUCUCGCAGGAUAUAAAUGGAGGUUUGCUAAAGGGGAGGAGAUGUGUUUGUGAG AAUACUGCUGAGAGAGUUCUGGAAGAGAAAAAAAGGAGGCAAUGGAAGGCGUUUGCUGGGAAAAGAGAAGAGCCAUGACU GCAUCUGUUGUUUCAAGGCCAGUUUUAUUAACCGCCUAUGUCAUAGAGGCGUUUUUUUUGGAGGGAUUUGAAGAAUGCCG GCGGCAUCAAGAAACGGACUUGAUGGUUGACGCCUGUUUUUAAAGUUAGAGACGUCGCGACCCUCGCACUUGUGGAGUCG UUCUUGACUUUUACUUUGGUCGCUUGAUGUUUCUCUCGUCUUCCCGUUCGCUCUU Z36099.1 U6 snRNA (small nuclear RNA) Saccharomyces cerevisiae 0.035883175999999996 1 GUUCGCGAAGUAACCCUUCGUGGACAUUUGGUCAAUUUGAAACAAUACAGAGAUGAUCAGCAGUUCCCCUGCAUAAGGAU GAACCGUUUUACAAAGAGAUUUAUUUCGUUUU CP007856.1 Pre-mRNA-splicing factor 8 Saccharomyces cerevisiae 0.279867469 1 LEVO MSGLPPPPPGFEEDSDLALPPPPPPPPGYEIEELDNPMVPSSVNEDTFLPPPPPPPSNFEINAEEIVDFTLPPPPPPPGL DELETKAEKKVELHGKRKLDIGKDTFVTRKSRKRAKKMTKKAKRSNLYTPKAEMPPEHLRKIINTHSDMASKMYNTDKKA FLGALKYLPHAILKLLENMPHPWEQAKEVKVLYHTSGAITFVNETPRVIEPVYTAQWSATWIAMRREKRDRTHFKRMRFP PFDDDEPPLSYEQHIENIEPLDPINLPLDSQDDEYVKDWLYDSRPLEEDSKKVNGTSYKKWSFDLPEMSNLYRLSTPLRD EVTDKNYYYLFDKKSFFNGKALNNAIPGGPKFEPLYPREEEEDYNEFNSIDRVIFRVPIRSEYKVAFPHLYNSRPRSVRI PWYNNPVSCIIQNDEEYDTPALFFDPSLNPIPHFIDNNSSLNVSNTKENGDFTLPEDFAPLLAEEEELILPNTKDAMSLY HSPFPFNRTKGKMVRAQDVALAKKWFLQHPDEEYPVKVKVSYQKLLKNYVLNELHPTLPTNHNKTKLLKSLKNTKYFQQT TIDWVEAGLQLCRQGHNMLNLLIHRKGLTYLHLDYNFNLKPTKTLTTKERKKSRLGNSFHLMRELLKMMKLIVDTHVQFR LGNVDAFQLADGIHYILNHIGQLTGIYRYKYKVMHQIRACKDLKHIIYYKFNKNLGKGPGCGFWQPAWRVWLNFLRGTIP LLERYIGNLITRQFEGRSNEIVKTTTKQRLDAYYDLELRNSVMDDILEMMPESIRQKKARTILQHLSEAWRCWKANIPWD VPGMPAPIKKIIERYIKSKADAWVSAAHYNRERIKRGAHVEKTMVKKNLGRLTRLWIKNEQERQRQIQKNGPEITPEEAT TIFSVMVEWLESRSFSPIPFPPLTYKNDTKILVLALEDLKDVYASKVRLNASEREELALIEEAYDNPHDTLNRIKKYLLT QRVFKPVDITMMENYQNISPVYSVDPLEKITDAYLDQYLWYEADQRKLFPNWIKPSDSEIPPLLVYKWTQGINNLSEIWD VSRGQSAVLLETTLGEMAEKIDFTLLNRLLRLIVDPNIADYITAKNNVVINFKDMSHVNKYGLIRGLKFASFIFQYYGLV IDLLLLGQERATDLAGPANNPNEFMQFKSKEVEKAHPIRLYTRYLDRIYMLFHFEEDEGEELTDEYLAENPDPNFENSIG YNNRKCWPKDSRMRLIRQDVNLGRAVFWEIQSRVPTSLTSIKWENAFVSVYSKNNPNLLFSMCGFEVRILPRQRMEEVVS NDEGVWDLVDERTKQRTAKAYLKVSEEEIKKFDSRIRGILMASGSTTFTKVAAKWNTSLISLFTYFREAIVATEPLLDIL VKGETRIQNRVKLGLNSKMPTRFPPAVFYTPKELGGLGMISASHILIPASDLSWSKQTDTGITHFRAGMTHEDEKLIPTI FRYITTWENEFLDSQRVWAEYATKRQEAIQQNRRLAFEELEGSWDRGIPRISTLFQRDRHTLAYDRGHRIRREFKQYSLE RNSPFWWTNSHHDGKLWNLNAYRTDVIQALGGIETILEHTLFKGTGFNSWEGLFWEKASGFEDSMQFKKLTHAQRTGLSQ IPNRRFTLWWSPTINRANVYVGFLVQLDLTGIFLHGKIPTLKISLIQIFRAHLWQKIHESIVFDICQILDGELDVLQIES VTKETVHPRKSYKMNSSAADITMESVHEWEVSKPSLLHETNDSFKGLITNKMWFDVQLRYGDYDSHDISRYVRAKFLDYT TDNVSMYPSPTGVMIGIDLAYNMYDAYGNWFNGLKPLIQNSMRTIMKANPALYVLRERIRKGLQIYQSSVQEPFLNSSNY AELFNNDIKLFVDDTNVYRVTVHKTFEGNVATKAINGCIFTLNPKTGHLFLKIIHTSVWAGQKRLSQLAKWKTAEEVSAL VRSLPKEEQPKQIIVTRKAMLDPLEVHMLDFPNIAIRPTELRLPFSAAMSIDKLSDVVMKATEPQMVLFNIYDDWLDRIS SYTAFSRLTLLLRALKTNEESAKMILLSDPTITIKSYHLWPSFTDEQWITIESQMRDLILTEYGRKYNVNISALTQTEIK DIILGQNIKAPSVKRQKMAELEAARSEKQNDEEAAGASTVMKTKTINAQGEEIVVVASADYESQTFSSKNEWRKSAIANT LLYLRLKNIYVSADDFVEEQNVYVLPKNLLKKFIEISDVKIQVAAFIYGMSAKDHPKVKEIKTVVLVPQLGHVGSVQISN IPDIGDLPDTEGLELLGWIHTQTEELKFMAASEVATHSKLFADKKRDCIDISIFSTPGSVSLSAYNLTDEGYQWGEENKD IMNVLSEGFEPTFSTHAQLLLSDRITGNFIIPSGNVWNYTFMGTAFNQEGDYNFKYGIPLEFYNEMHRPVHFLQFSELAG DEELEAEQIDVFS P33334 Protein CWC16 Saccharomyces cerevisiae 0.032371086 1 LEVO MSERKAINKYYPPDYNPLEAEKLSRKMAKKLKTMNKSHASIRLMTPFSMRCLECNEYIPKSRKFNGKKELLKEKYLDSIK IYRLTISCPRCANSIAFRTDPGNSDYVMEVGGVRNYVPQKPNDDLNAKTAVESIDETLQRLVREKEMEQNEKMGIKEQAD DKMDLLEKRLAKIQQEQEDDEELENLRKKNLEMSQRAEMINRSKHAQQEKAVTTDDLDNLVDQVFDNHRQRTNKPGNNND EKRTPLFNPTSTKGKIQKKSSVRTNPLGIVIKRGKSLK P28320 Pre-mRNA-splicing factor CWC25 Saccharomyces cerevisiae 0.020412477 1 LEVO MGSGDLNLLKSWNPKLMKNRKKVWETEQDLITEQQKLNTRLKEIEKERELNELLNESSKDKPETLKNDLALKKSGLEWMY QDAKLSDEKEDYLLGKKKLDSSILNQPATPPVRAATTISASGAATSISSQKKKSKLLKDDPMSKFKVTKQQRRTPDSTKK RAMSQRGKPLSKPAPDLDY P53854 Pre-mRNA-splicing factor SNU114 Saccharomyces cerevisiae 0.114174008 1 LEVO MEGDDLFDEFGNLIGVDPFDSDEEESVLDEQEQYQTNTFEGSGNNNEIESRQLTSLGSKKELGISLEHPYGKEVEVLMET KNTQSPQTPLVEPVTERTKLQEHTIFTQLKKNIPKTRYNRDYMLSMANIPERIINVGVIGPLHSGKTSLMDLLVIDSHKR IPDMSKNVELGWKPLRYLDNLKQEIDRGLSIKLNGSTLLCTDLESKSRMINFLDAPGHVNFMDETAVALAASDLVLIVID VVEGVTFVVEQLIKQSIKNNVAMCFVINKLDRLILDLKLPPMDAYLKLNHIIANINSFTKGNVFSPIDNNIIFASTKLGF TFTIKEFVSYYYAHSIPSSKIDDFTTRLWGSVYYHKGNFRTKPFENVEKYPTFVEFILIPLYKIFSYALSMEKDKLKNLL RSNFRVNLSQEALQYDPQPFLKHVLQLIFRQQTGLVDAITRCYQPFELFDNKTAHLSIPGKSTPEGTLWAHVLKTVDYGG AEWSLVRIYSGLLKRGDTVRILDTSQSESRQKRQLHDISKTETSNEDEDEDDETPSCEVEEIGLLGGRYVYPVHEAHKGQ IVLIKGISSAYIKSATLYSVKSKEDMKQLKFFKPLDYITEAVFKIVLQPLLPRELPKLLDALNKISKYYPGVIIKVEESG EHVILGNGELYMDCLLYDLRASYAKIEIKISDPLTVFSESCSNESFASIPVSNSISRLGEENLPGLSISVAAEPMDSKMI QDLSRNTLGKGQNCLDIDGIMDNPRKLSKILRTEYGWDSLASRNVWSFYNGNVLINDTLPDEISPELLSKYKEQIIQGFY WAVKEGPLAEEPIYGVQYKLLSISVPSDVNIDVMKSQIIPLMKKACYVGLLTAIPILLEPIYEVDITVHAPLLPIVEELM KKRRGSRIYKTIKVAGTPLLEVRGQVPVIESAGFETDLRLSTNGLGMCQLYFWHKIWRKVPGDVLDKDAFIPKLKPAPIN SLSRDFVMKTRRRKGISTGGFMSNDGPTLEKYISAELYAQLRENGLVP P36048 ISY1 Saccharomyces cerevisiae 0.028120896 1 LEVO MSRNVDKANSVLVRFQEQQAESAGGYKDYSRYQRPRNVSKVKSIKEANEWKRQVSKEIKQKSTRIYDPSLNEMQIAELND ELNNLFKEWKRWQWHIDHTLMEKKTKRKRLEDSHVLMNSGKLINGKRYFGRALELPEVREWLKQSQRQNDGGSINTKCIP KDRNDFYYHGKVTAALTEFEANWTSILKAHYNVPVNEDEEEMSRQTQEIRVPTLADMEHWLVQRRKKKLMDELNL A0A165UGV0 CWC22 Saccharomyces cerevisiae 0.069118984 1 LEVO MSTATIQDEDIKFQRENWEMIRSHVSPIISNLTMDNLQESHRDLFQVNILIGRDIICKNVVDFTLNKQNGRLIPALSALI ALLNSDIPDIGETLAKELMLMFVQQFNRKDYVSCGNILQCLSILFLYDVIHEIVILQILLLLLEKNSLRLVIAVMKICGW KLALVSKKTHDMIWEKLRYILQTQELSSTLRESLETLFEIRQKDYKSGSQGLFILDPTSYTVHTHSYIVSDEDEANKELG NFEKCENFNELTMAFDTLRQKLLINNTSDTNEGSNSQLQIYDMTSTNDVEFKKKIYLVLKSSLSGDEAAHKLLKLKIANN LKKSVVDIIIKSSLQESTFSKFYSILSERMITFHRSWQTAYNETFEQNYTQDIEDYETDQLRILGKFWGHLISYEFLPMD CLKIIKLTEEESCPQGRIFIKFLFQELVNELGLDELQLRLNSSKLDGMFPLEGDAEHIRYSINFFTAIGLGLLTEDMRSR LTIIQEVEDAEEEEKKLREEEELEKLRKKARESQPTQGPKIHESRLFLQNDTRDNSRSRSPFTVETRKRARSRTPPRGSR NHRNRSRTPPRRPKNHRNRSRTPPARRQRHR A0A162ERE7 PRP46 Saccharomyces cerevisiae 0.050801316 1 LEVO MDGNDHKVENLGDVDKFYSRIRWNNQFSYMATLPPHLQSEMEGQKSLLMRYDTYRKESSSFSGEGKKVTLQHVPTDFSET SQAVISKKDHDTHASAFVNKIFQPEVAEELIVNRYEKLLSQRPEWHAPWKLSRVINGHLGWVRCVAIDPVDNEWFITGSN DTTMKVWDLATGKLKTTLAGHVMTVRDVAVSDRHPYLFSVSEDKTVKCWDLEKNQIIRDYYGHLSGVRTVSIHPTLDLIA TAGRDSVIKLWDMRTRIPVITLVGHKGPINQVQCTPVDPQVVSSSTDATVRLWDVVAGKTMKVLTHHKRSVRATALHPKE FSVASACTDDIRSWGLAEGSLLTNFESEKTGIINTLSINQDDVLFAGGDNGVLSFYDYKSGHKYQSLATREMVGSLEGER SVLCSTFDKTGLRLITGEADKSIKIWKQDETATKESEPGLAWNPNLSAKRF A0A162HKW4 Pre-mRNA-processing protein 45 Saccharomyces cerevisiae 0.042548726999999995 1 LEVO MFSNRLPPPKHSQGRVSTALSSDRVEPAILTDQIAKNVKLDDFIPKRQSNFELSVPLPTKAEIQECTARTKSYIQRLVNA KLANSNNRASSRYVTETHQAPANLLLNNSHHIEVVSKQMDPLLPRFVGKKARKVVAPTENDEVVPVLHMDGSNDRGEADP NEWKIPAAVSNWKNPNGYTVALERRVGKALDNENNTINDGFMKLSEALENADKKARQEIRSKMELKRLAMEQEMLAKESK LKELSQRARYHNGTPQTGAIVKPKKQTSTVARLKELAYSQGRDVSEKIILGAAKRSEQPDLQYDSRFFTRGANASAKRHE DQVYDNPLFVQQDIESIYKTNYEKLDEAVNVKSEGASGSHGPIQFTKAESDDKSDNYGA P28004 Pre-mRNA-splicing factor BUD31 Saccharomyces cerevisiae 0.018484502 1 LEVO MPRIKTRRSKPAPDGFEKIKPTLTDFEIQLRDAQKDKSSKLAAKSNEQLWEIMQLHHQRSRYIYTLYYKRKAISKDLYDW LIKEKYADKLLIAKWRKTGYEKLCCLRCIQKNETNNGSTCICRVPRAQLEEEARKKGTQVSFHQCVHCGCRGCASTD P25337 CWC2 Saccharomyces cerevisiae 0.038458508 1 LEVO MTSWRDKSAKVQVKESELPSSIPAQTGLTFNIWYNKWSQGFAGNTRFVSPFALQPQLHSGKTRGDNDGQLFFCLFFAKGM CCLGPKCEYLHHIPDEEDIGKLALRTEALDCFGREKFADYREDMGGIGSFRKKNKTLYVGGIDGALNSKHLKPAQIESRI RFVFSRLGDIDRIRYVESKNCGFVKFKYQANAEFAKEAMSNQTLLLPSDKEWDDRREGTGLLVKWANEDPDPAAQKRLQE ELKLESLNMMVHLINNNTNSAGTEVNNKNNERLDRTFPEASVDNVKKRLLPLDNGMESDDFIEKLKKVKKNISRENISSK PSVGKLGGPLLDYLSSDED A0A162HWE4 Pre-mRNA-splicing factor SLT11 Saccharomyces cerevisiae 0.04098858999999999 1 LEVO MNDEINEPPPNICEQCLGDEANIRMTKIPQGSECKICTLPFTLYHFKTSKRSNNIIKTLICVRCATQRNICQCCMLDSRW HIPIQLRDHLISLVNEENVMTEEAKNDMMKRFLSLKNVKLGGAQITSDPSEADNIVDKLKNILLRATSDGPSTPLIKNTT ALYKNEKGANEVKNLEKYASVDISHILKKLPLNESFLKNPSTKSFFLYNIDASIPEWKITDTVSQLLGIKKWKDGNSLSL IVNHKAKCGGLRFQSSELGERFVSKISETLVTPKGLKRGVLLIDRFRIFIIPWSSGFSAASFGTNTAENIKLSLSLNKLI QLELGLSFPTKSTDNAKNDKKKTSKKVHKDRSKKSKPRANKLTI P38241 CEF1 Saccharomyces cerevisiae 0.067819789 1 LEVO MPPVPIYVKGGVWTNVEDQILKAAVQKYGTHQWSKVASLLQKKTARQSELRWNEYLNPKLNFTEFSKEEDAQLLDLAREL PNQWRTIADMMARPAQVCVERYNRLLESEDSGGAALSTGVTDLKVGDINPNAETQMARPDNGDLEDEEKEMLAEARARLL NTQGKKATRKIRERMLEESKRIAELQKRRELKQAGINVAIKKPKKKYGTDIDYNEDIVYEQAPMPGIYDTSTEDRQIKKK FEQFERKVNRKGLDGNKDKPSKKNKDKKRKHDENEHVEKAALGEPTTLTDEYKKPKLILSAPGTKQGKVTYKKKLESKRQ KLIEAQATGTVLTPKELLPHEPGQEDNERSNIKSGKQLKSRIRKFLVQMFASLPSPKNDFEIVLSEDEKEEDAEIAEYEK EFENERAMNEEDNFIESPSQNDAPPVSLVAVPLAYSTLPIPEFKNNPQSAIDNKYNLLVANAINKEPHMVPEDTVDFLKE VESRMQHITQGRTSMKIQFKTAMPPTEVLLESIQSKVESIEQLQRKLQQVQPLEQQNNEMCSTLCHHSLPALIEGQRKYY ADYYAYRQEIRSLEGRRKRLQAMLNSSSSI A0A165TLN2 CWC15 Saccharomyces cerevisiae 0.019970195 1 LEVO MTTSHRPQLEARSGAKAAAYTPTGIEHARLLPGHTTLKYRKFKEEENLKANCAQEDRNNDKSLEEVVVNEEKQDVVGSGN LQETRSEKDQKDSLQELLVTQKNKVEDKAELEGNEQLKGGNSSRRSWRKGTAFGRHKVTKETNIKEHATKKSASGYINDM TKSEYHQEFLHKHVR A0A162GIZ3 Pre-mRNA-splicing factor CWC21 Saccharomyces cerevisiae 0.015793596 1 LEVO MSYNGIGLKSAKGSSTSGHVQRSLASNNRRRPQGSQQQRQQRQNAIKKASHDKASRPLAVQKQIETHMEKREIEVQVSEL RDRLEEEETLSEEQIDKKCEALRAKLTNEWQEQQRMSSLYTPRKARLTEEQHRHE Q03375 CLF1 Saccharomyces cerevisiae 0.082532867 1 LEVO MDTLEPTAVDTHVSAEQILRDVYKKGQKARGSTNIDILDLEELREYQRRKRTEYEGYLKRNRLDMGQWIRYAQFEIEQHD MRRARSIFERALLVDSSFIPLWIRYIDAELKVKCINHARNLMNRAISTLPRVDKLWYKYLIVEESLNNVEIVRSLYTKWC SLEPGVNAWNSFVDFEIRQKNWNGVREIYSKYVMAHPQMQTWLKWVRFENRHGNTEFTRSVYSLAIDTVANLQNLQIWSD MEVAKLVNSFAHWEAAQQEYERSSALYQVAIEKWPSNQLLKAGLLDFEKQFGDINSIEETISYKRKMDYETILSNNAYDY DTWWLYLDLISESFPKQIMQTFEKAIVDSRPKELSKNVQWKRYIYLWMRYICYVELELENSLLEEELFQRLIDDIIPHKH FTFSKIWLMYAKFLIRHDDVPKARKILGKAIGLCPKAKTFKGYIELEVKLKEFDRVRKIYEKFIEFQPSDLQIWSQYGEL EENLGDWDRVRGIYTIALDENSDFLTKEAKIVLLQKYITFETESQEFEKARKLYRRYLELNQYSPQSWIEFAMYQTSTPT KQQLLDLAKLQSENVDEDIEFEITDENKLEARKVFEEAIVFFKEKDDKQGRLSIMEALKDYEETYGTELDQETVKKRFPK VIKKVRLQDGVEEEFVDYVFPDDIDDDKPKPSKFLELAKKWKQEQAL A0A165TU20 SYF1 Saccharomyces cerevisiae 0.100356141 1 LEVO MSAYIAMKGVITNVDENIRNDEDVAFEYEIQKTPQNILTWKRYIEYWKEEGRTDKQIRWLYERFCSQFVTDTSIWEDYIR WESTKEVVETSRIFWLFQRCLKSCVRDCDRICLSYLELAIEQYDLAMIRHALASSLMKMEREMHRKVWDPVIKFVEEKVL PLTQLDSTQEDEEESTDEAELINVLLVKGFTKGGFISEEISENGSRGDIWSSHILERYLKVAPQQKRNESLATLALTRDN ITIKSVYEKYLPQDENSGKYLPSSELPFELNFNYLASLEKLGLDNQYEEFMRQMNGIYPDKWLFLILSLAKYYISRGRLD SCGDLLKKSLQQTLRYSDFDRIYNFYLLFEQECSQFILGKLKENDSKFFNQKDWTEKLQAHMATFESLINLYDIYLNDVA LRQDSNLVETWMKRVSLQKSAAEKCNVYSEAILKIDPRKVGTPGSFGRLWCSYGDLYWRSNAISTARKLWTQSLKVPYPY IEDLEEIYLNWADRELDKEGVERAFSILEDALHVPTNPEILLEKYKNGHRKIPAQTVLFNSLRIWSKYIDYLEAYCPKDA NSSDKIFNKTKMAYNTVIDLRLITPAMAENFALFLQNHYEVMESFQVYEKTIPLFPPEIQYELWIEYLEVATSHQLSSLS PEHIRFLFEKALKNLCSNGIDCKTIFIAYSVFEERISGLISKSIEILRRGAVIGIVSVSTHLESRLQLWRMCISKAESTL GPSVTRELYQECIQILPNSKAVEFVIKFSDFESSIGETIRAREILAYGAKLLPPSRNTELWDSFEIFELKHGDKETYKDM LKMKKVLESNMLIDSASVSHEEGNINFVAAATSHAPNSHTLTQSTSSYSINPDEIELDI A0A165VVY6 Small nuclear ribonucleoprotein-associated protein B Saccharomyces cerevisiae 0.02242699 2 LEVO MSKIQVAHSSRLANLIDYKLRVLTQDGRVYIGQLMAFDKHMNLVLNECIEERVPKTQLDKLRPRKDSKDGTTLNIKVEKR VLGLTILRGEQILSTVVEDKPLLSKKERLVRDKKEKKQAQKQTKLRKEKEKKPGKIAKPNTANAKHTSSNSREIAQPSSS RYNGGNDNIGANRSRFNNEAPPQTRKFQPPPGFKRK P40018 Small nuclear ribonucleoprotein Sm D3 Saccharomyces cerevisiae 0.011240138999999998 2 LEVO MTMNGIPVKLLNEAQGHIVSLELTTGATYRGKLVESEDSMNVQLRDVIATEPQGAVTHMDQIFVRGSQIKFIVVPDLLKN APLFKKNSSRPMPPIRGPKRR P43321 Small nuclear ribonucleoprotein E Saccharomyces cerevisiae 0.010385097999999999 2 LEVO MSNKVKTKAMVPPINCIFNFLQQQTPVTIWLFEQIGIRIKGKIVGFDEFMNVVIDEAVEIPVNSADGKEDVEKGTPLGKI LLKGDNITLITSAD Q12330 Small nuclear ribonucleoprotein F Saccharomyces cerevisiae 0.009669945 2 LEVO MSESSDISAMQPVNPKPFLKGLVNHRVGVKLKFNSTEYRGTLVSTDNYFNLQLNEAEEFVAGVSHGTLGEIFIRCNNVLY IRELPN P54999 Small nuclear ribonucleoprotein G Saccharomyces cerevisiae 0.008490808999999998 2 LEVO MVSTPELKKYMDKKILLNINGSRKVAGILRGYDIFLNVVLDDAMEINGEDPANNHQLGLQTVIRGNSIISLEALDAI P40204 Small nuclear ribonucleoprotein Sm D1 Saccharomyces cerevisiae 0.016296798

MKLVNFLKKLRNEQVTIELKNGTTVWGTLQSVSPQMNAILTDVKLTLPQPRLNKLNSNGIAMASLYLTGGQQPTASDNIA SLQYINIRGNTIRQIILPDSLNLDSLLVDQKQLNSLRRSGQIANDPSKKRRRDFGAPANKRPRRGL

2 LEVO MKLVNFLKKLRNEQVTIELKNGTTVWGTLQSVSPQMNAILTDVKLTLPQPRLNKLNSNGIAMASLYLTGGQQPTASDNIA SLQYINIRGNTIRQIILPDSLNLDSLLVDQKQLNSLRRSGQIANDPSKKRRRDFGAPANKRPRRGL Q02260 Small nuclear ribonucleoprotein Sm D2 Saccharomyces cerevisiae 0.012876066 2 LEVO MSSQIIDRPKHELSRAELEELEEFEFKHGPMSLINDAMVTRTPVIISLRNNHKIIARVKAFDRHCNMVLENVKELWTEKK GKNVINRERFISKLFLRGDSVIVVLKTPVE Q06217 U2 small nuclear ribonucleoprotein A' Saccharomyces cerevisiae 0.027232252 1 LEVO MKFTPSIVIDAPQYYVDHFNGKYNVDKCVILRDLQLETDSESMPSSLKHLTKPTHILDLTNNDLIMIPDLSRRDDIHTLL LGRNNIVEVDGRLLPMNVQNLTLSNNSIRRFEDLQRLRRAPRTLKNLTLIGNQVCHLANYREHVLRLVPHLETLDFQNVT AEERKSAMSFPRQADGDTLGPVNTAIRDNGSRDKTMEIMNLVVSKMTVERRNELKKQLAEATSLEEIARLEKLLSGGV Q08963 U2 small nuclear ribonucleoprotein B'' Saccharomyces cerevisiae 0.012850944 1 LEVO MVEPARKKQRIDRDTHHTVAEPVTEAKNTLYVSQLNEKINMQRLRVNLFLLFATFGEVLKVSMNFKKQRGQAFITMRTID QASLAQISLNGERFFGKPLKVEFSKSETKTL P40567 unknown Saccharomyces cerevisiae 0.011251861 1 LEVO (UNK)(UNK)(UNK)(UNK)(UNK)(UNK)(UNK)(UNK)(UNK)(UNK)(UNK)(UNK)(UNK)(UNK)(UNK)(UNK) (UNK)(UNK)(UNK)(UNK)(UNK)(UNK)(UNK)(UNK)(UNK)(UNK)(UNK)(UNK)(UNK)(UNK)(UNK)(UNK) (UNK)(UNK)(UNK)(UNK)(UNK)(UNK)(UNK)(UNK)(UNK)(UNK)(UNK)(UNK)(UNK)(UNK)(UNK)(UNK) (UNK)(UNK)(UNK)(UNK)(UNK)(UNK)(UNK)(UNK)(UNK)(UNK)(UNK)(UNK)(UNK)(UNK)(UNK)(UNK) (UNK)(UNK)(UNK)(UNK)(UNK)(UNK)(UNK)(UNK)(UNK)(UNK)(UNK)(UNK)(UNK)(UNK)(UNK)(UNK) (UNK)(UNK)(UNK)(UNK)(UNK)(UNK)(UNK)(UNK)(UNK)(UNK)(UNK)(UNK)(UNK)(UNK)(UNK)(UNK) (UNK)(UNK)(UNK)(UNK)(UNK)(UNK)(UNK)(UNK)(UNK)(UNK)(UNK)(UNK)(UNK)(UNK)(UNK)(UNK) (UNK)(UNK)(UNK)(UNK)(UNK)(UNK)(UNK)(UNK)(UNK)(UNK)(UNK)(UNK)(UNK)(UNK)(UNK)(UNK) (UNK)(UNK)(UNK)(UNK) MAGNESIUM ION 2.4305e-05 2 MG ZINC ION 6.5409e-05 7 ZN GUANOSINE-5'-TRIPHOSPHATE 0.0005231799999999999 1 GTP singleParticle particle 0.3 7.8 20.0 Hepes.KOH pH 7.8 75.0 KCl potassium chloride 250.0 EDTA Quantifoil R2/2 COPPER 400 CARBON CONTINUOUS 6.0 GLOW DISCHARGE 30 AIR ETHANE 100 277 FEI VITROBOT MARK III

3 microlitres sample were applied to the grid, left for 30 seconds and then blotted for 2.5-3.0 seconds before plunging..

FEI TITAN KRIOS FLOOD BEAM BRIGHT FIELD FIELD EMISSION GUN 300 0.5 4.0 81000.0 35714.0 FEI TITAN KRIOS AUTOGRID HOLDER NITROGEN GIF Quantum GATAN K2 QUANTUM (4k x 4k) SUPER-RESOLUTION 1-20 2213 0.8 2.0

Total dose: 40 electrons/Angstrom^2 over 16 seconds. 20 movie frames collected at 1.25 frames per second.

1 248000 CTFFIND 4 PHASE FLIPPING AND AMPLITUDE CORRECTION EMD-6413

Intron-lariat spliceosome complex low-pass filtered to 60 Angstrom

1 C1 3.8 FSC 0.143 CUT-OFF RELION 1.4 93106 PROJECTION MATCHING RELION 1.4 PROJECTION MATCHING RELION 1.4 RELION 1.4 OTHER

Used secondary structure restraints generated in ProSMART and LibG.

RECIPROCAL