DOCK (dedicator of cytokinesis) proteins are guanine nucleotide exchange factors (GEFs) that activate some small GTPases, such as Rac or Cdc42, by exchanging bound GDP for free GTP to control cell migration, morphogenesis, and phagocytosis. These proteins share a DOCK-type C2 domain (also termed the DOCK-homology region (DHR)-1) at the N-terminal, and the DHR-2 domain (also termed the DOCKER domain) at the C-terminal. DHR-2 is the GEF catalytic domain organised into three lobes A, B and C, with the Rho-family binding site and catalytic centre generated entirely from lobes B and C. This entry represents Lobe B which adopts an unusual architecture of two antiparallel beta sheets disposed in a loosely packed orthogonal arrangement. This lobe changes its position relative to lobe C and the bound GTPase, which suggests that lobe B distinguishes between the switch 1 conformations of Rac1 and Cdc42 [2].

1: Structure of the DOCK2-ELMO1 complex provides insights into regulation of the auto-inhibited state. Chang L, Yang J, Jo CH, Boland A, Zhang Z, McLaughlin SH, Abu-Thuraia A, Killoran RC, Smith MJ, Cote JF, Barford D; Nat Commun. 2020;11:3464. PMID:32651375

2: Structural Basis for the Dual Substrate Specificity of DOCK7 Guanine Nucleotide Exchange Factor. Kukimoto-Niino M, Tsuda K, Ihara K, Mishima-Tsumagari C, Honda K, Ohsawa N, Shirouzu M; Structure. 2019;27:741-748. PMID:30853411