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From Proteopedia
Crystal structure of the C-terminal ARM domain of Homo sapiens SPIN90 (SH3-protein interacting with Nck), residues 351-722
Structural highlights
Disease[SPN90_HUMAN] A chromosomal aberration involving NCKIPSD/AF3p21 is found in therapy-related leukemia. Translocation t(3;11)(p21;q23) with KMT2A/MLL1.[1] Function[SPN90_HUMAN] Has an important role in stress fiber formation induced by active diaphanous protein homolog 1 (DRF1). Induces microspike formation, in vivo (By similarity). In vitro, stimulates N-WASP-induced ARP2/3 complex activation in the absence of CDC42 (By similarity). May play an important role in the maintenance of sarcomeres and/or in the assembly of myofibrils into sarcomeres. Implicated in regulation of actin polymerization and cell adhesion. Plays a role in angiogenesis.[2] Publication Abstract from PubMedUnlike the WASP family of Arp2/3 complex activators, WISH/DIP/SPIN90 (WDS) family proteins activate actin filament nucleation by the Arp2/3 complex without the need for a preformed actin filament. This allows WDS proteins to initiate branched actin network assembly by providing seed filaments that activate WASP-bound Arp2/3 complex. Despite their important role in actin network initiation, it is unclear how WDS proteins drive the activating steps that require both WASP and pre-existing actin filaments during WASP-mediated nucleation. Here, we show that SPIN90 folds into an armadillo repeat domain that binds a surface of Arp2/3 complex distinct from the two WASP sites, straddling a hinge point that may stimulate movement of the Arp2 subunit into the activated short-pitch conformation. SPIN90 binds a surface on Arp2/3 complex that overlaps with actin filament binding, explaining how it could stimulate the same structural rearrangements in the complex as pre-existing actin filaments. By revealing how WDS proteins activate the Arp2/3 complex, these data provide a molecular foundation to understand initiation of dendritic actin networks and regulation of Arp2/3 complex by its activators. Structure of the nucleation-promoting factor SPIN90 bound to the actin filament nucleator Arp2/3 complex.,Luan Q, Liu SL, Helgeson LA, Nolen BJ EMBO J. 2018 Oct 15. pii: embj.2018100005. doi: 10.15252/embj.2018100005. PMID:30322896[3] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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