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Overview

Uniprot ID	Q9HCN4
Protein Name	GPN-loop GTPase 1
Gene Name	GPN1
Organism	Homo sapiens

Kla Sites from experimental identification

Position	Flanking peptide
297	EQLERLRKDMGSVAL

Function

Small GTPase involved in the correct assembly of RNA polymerase II (RNAPII) complex, ensuring proper nuclear import of RNAPII (PubMed:11058119, PubMed:20855544, PubMed:21768307, PubMed:28153773). In vitro, exhibits a chaperone-like activity and a chaperone substrate protein can stimulate its GTPase activity. It is proposed to bind exposed hydrophobic peptide regions of newly synthesized RNAP II subunit, triggering the opening of a hydrophobic pocket in its GDP-bound state. This interaction likely traps exposed hydrophobic regions, preventing misassembly and providing a time window for association with the cognate RNAP II subunit. Peptide binding promotes GDP release, and increasing GTP affinity to facilitate GTP rebinding. Subsequent GTP hydrolysis would then lead to the release of the bound RNAP II subunit to enable association with cognate subunits and RNAP II assembly (By similarity). Forms an interface between the RNA polymerase II enzyme and chaperone/scaffolding proteins, suggesting that it is required to connect RNA polymerase II to regulators of protein complex formation (PubMed:17643375). May be involved in nuclear localization of XPA (PubMed:11058119)

Protein Sequence

10 MAASAAAAEL 20 QASGGPRHPV 30 CLLVLGMAGS 40 GKTTFVQRLT 50 GHLHAQGTPP 60 YVINLDPAVH 70 EVPFPANIDI 80 RDTVKYKEVM 90 KQYGLGPNGG 100 IVTSLNLFAT 110 RFDQVMKFIE 120 KAQNMSKYVL 130 IDTPGQIEVF 140 TWSASGTIIT 150 EALASSFPTV 160 VIYVMDTSRS 170 TNPVTFMSNM 180 LYACSILYKT 190 KLPFIVVMNK 200 TDIIDHSFAV 210 EWMQDFEAFQ 220 DALNQETTYV 230 SNLTRSMSLV 240 LDEFYSSLRV 250 VGVSAVLGTG 260 LDELFVQVTS 270 AAEEYEREYR 280 PEYERLKKSL 290 ANAESQQQRE 300 QLERLRKDMG 310 SVALDAGTAK 320 DSLSPVLHPS 330 DLILTRGTLD 340 EEDEEADSDT 350 DDIDHRVTEE 360 SHEEPAFQNF 370 MQESMAQYWK RNNK

Gene Ontology

Classification	GO ID	Description
Cellular Component	GO:0005737	cytoplasm
Cellular Component	GO:0005829	cytosol
Cellular Component	GO:0005654	nucleoplasm
Cellular Component	GO:0005634	nucleus
Molecular Function	GO:0005525	GTP binding
Molecular Function	GO:0003924	GTPase activity
Molecular Function	GO:0046872	metal ion binding
Molecular Function	GO:0000993	RNA polymerase II complex binding
Biological Process	GO:0006606	protein import into nucleus

Reference

[1] He C, Zhang J, Bai X, Lu C, Zhang K. Lysine lactylation-based insight to understanding the characterization of cervical cancer.. Biochim Biophys Acta Mol Basis Dis 1870(7):167356. 2024 Oct. PMID: 39025375.

[2] He J, Lai T, Zhou Z, Yang H, Lei Z et al.. Multiomics profiling reveals the involvement of protein lactylation in nonhomologous end joining pathway conferring radioresistance in lung adenocarcinoma cell.. Sci Rep 15(1):24651. 2025 Jul 9. PMID: 40634431.