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Protein-interacting V-domain of mammalian Alix and related domains This superfamily contains the V-shaped (V) domain of mammalian Alix (apoptosis-linked gene-2 interacting protein X), His-Domain type N23 protein tyrosine phosphatase (HD-PTP, also known as PTPN23), Bro1 and Rim20 (also known as PalA) from Saccharomyces cerevisiae, and related domains. Alix, HD-PTP, Bro1, and Rim20 all interact with the ESCRT (Endosomal Sorting Complexes Required for Transport) system. Alix, also known as apoptosis-linked gene-2 interacting protein 1 (AIP1), participates in membrane remodeling processes during the budding of enveloped viruses, vesicle budding inside late endosomal multivesicular bodies (MVBs), and the abscission reactions of mammalian cell division. It also functions in apoptosis. HD-PTP functions in cell migration and endosomal trafficking, Bro1 in endosomal trafficking, and Rim20 in the response to the external pH via the Rim101 pathway. The Alix V-domain contains a binding site, partially conserved in this superfamily, for the retroviral late assembly (L) domain YPXnL motif. The Alix V-domain is also a dimerization domain. Members of this superfamily have an N-terminal Bro1-like domain, which binds components of the ESCRT-III complex. The Bro1-like domains of Alix and HD-PTP can also bind human immunodeficiency virus type 1 (HIV-1) nucleocapsid. Many members, including Alix, HD-PTP, and Bro1, also have a proline-rich region (PRR), which binds multiple partners in Alix, including Tsg101 (tumor susceptibility gene 101, a component of ESCRT-1) and the apoptotic protein ALG-2. The C-terminal portion (V-domain and PRR) of Bro1 interacts with Doa4, a ubiquitin thiolesterase needed to remove ubiquitin from MVB cargoes; it interacts with a YPxL motif in Doa4s catalytic domain to stimulate its deubiquitination activity. Rim20 may bind the ESCRT-III subunit Snf7, bringing the protease Rim13 (a YPxL-containing transcription factor) into proximity with Rim101, and promoting the proteolytic activation of Rim101. HD-PTP is encoded by the PTPN23 gene, a tumor suppressor gene candidate often absent in human kidney, breast, lung, and cervical tumors. HD-PTP has a C-terminal catalytically inactive tyrosine phosphatase domain. |
Jiyao W et al.(2023). "The conserved domain database in 2023.",