This entry represents the luminal domain (LD) found in eukaryotic V-type proton ATPase subunit S1 involved in V-ATPase V0 assembly, including Ac45 subunit (ATP6AP1) [1,2]. This domain folds as a globular beta-prism structure which is structurally similar to LAMP1-3, thus, the LD domain of Ac45 is an evolutionarily conserved member of the LAMP family [2]. Ac45 is an ER membrane protein that guides the V-type ATPase into specialised subcellular compartments [3] and is critical for Vo complex assembly as it connects to multiple Vo subunits and phospholipids in the c-ring [2]. Missense mutations in the X-linked ATP6AP1 gene cause immunodeficiency in males that leads to recurrent bacterial infection, hepatopathy, cognitive impairment, and abnormal protein glycosylation [2].

1: A novel accessory subunit for vacuolar H(+)-ATPase from chromaffin granules. Supek F, Supekova L, Mandiyan S, Pan YC, Nelson H, Nelson N; J Biol Chem 1994;269:24102-24106. PMID:7929063

2: Structures of a Complete Human V-ATPase Reveal Mechanisms of Its Assembly. Wang L, Wu D, Robinson CV, Wu H, Fu TM; Mol Cell. 2020;80:501-511. PMID:33065002

3: The vacuolar-ATPase complex and assembly factors, TMEM199 and CCDC115, control HIF1alpha prolyl hydroxylation by regulating cellular iron levels. Miles AL, Burr SP, Grice GL, Nathan JA; Elife. 2017; [Epub ahead of print] PMID:28296633