A switch I mutant of Cdc42 exhibits less conformational freedom.

摘要: The success of target-based approaches to combat Ras-related signal transduction events leading diseases such as cancer will depend upon understanding the correlations among structural biology, protein-protein interactions and protein function. Indeed, binding activation receptors may play a role in abnormal cell-signaling activities. Understanding activities require that elucidate changes both conformation dynamics lead particular molecular behaviors. Cdc42 is member Rho subfamily Ras proteins are closely related small GTPases. These ubiquitously expressed, evolutionarily conserved, first human oncogenic have been identified (1, 2). Mutations or expression patterns found up 30% cell types act switches couple extracellular signals variety cellular responses. controlled via cycling between biologically active GTP form an inactive GDP-bound 3). function Cdc42, well other proteins, largely mediated through interactions. Therefore, specificity governing these interactions, associated conformational vital for mechanisms underlying onset cancer. Different can activate guanine nucleotide exchange factors (GEFs) induce G-protein switch from inactive, state active, GTP-bound (4, 5). In state, GTPase binds downstream effector turn mediate diverse biological different terminated when deactivated, either its own ability hydrolyze GTP, by means reaction catalyzed GTPase-activating (GAPs) (6). Alternatively, with regulatory block GDP dissociation, dissociation inhibitors (GDIs), stabilize prevent effective GTP-GDP (7). Mechanisms which most participate proliferation and/or transformation include mutations alter activity 8–11) effectors regulators (12). best understood those result inhibiting 8). addition this, also shown facilitate increasing rate forms (13 199). Structural studies mutant Cdc42(F28L) provided evidence local environmental affect stability nucleotide-binding site aberrant behavior (14). The molecules essentially involves two regions: Switch I (residues 28–40) II 57–74), undergo rapid changes. fact, it has reported region H-Ras possesses distinct states, bound effectors, unbound (15, 16). principal interacting surface (11, 17). For solution, several resonances regions cannot be observed due increased flexibility (18). results loss backbone mobility region, suggesting inherent allow bind (19). It widely thought freedom provide basis nucleotide-dependent propagation this central engagement (17, 20, 21). This premise agrees (22). implicated Thr35 being critical completely invariant proteins. 31P-NMR H-Ras(T35A) Cdc42(T35A) suggested mutation causes signaling-defective spectra their revealed only changes, was similar wild type. However, peptide target produced significant shifts 31P type complexes but not T35A-effector complexes, weaker interaction derivatives 16). To investigate importance we determined solution structure, examined dynamics, characterized biochemical (2kb0.pdb). Our suggest leads relative rest protein. furthermore details on why inherently important recognition effectors. Recent implied innovative strategies treatment future should specific directly potential, example using antibody fragments (23). Taken together, structure that, Ras-protein restrict inhibition signaling therapeutic potential.