Plant biology

CRIB Required for GAP Activity

Science's STKE  09 Jan 2001:
Vol. 2001, Issue 64, pp. tw14
DOI: 10.1126/stke.2001.64.tw14

In plants, several signal transduction pathways are influenced by the small guanosine triphosphatase (GTPase) Rop. Wu, Li, and Yang identified five Rop GTPase-activating proteins (RopGAPs) by two-hybrid analysis and by searching for proteins with sequence similarity. The proteins all have a conserved GAP motif, a Rho GTPase-binding Cdc42/Rac-interactive binding (CRIB) domain, and an SH3 domain. Unlike mammalian CRIB domain-containing proteins, which inhibit GAP activity, the GAP activity of the RopGAPs required the CRIB domain, which appeared to enhance the interaction between Rop and the GAP protein. Experiments with the CRIB domain or GAP domain fused with maltose-binding protein showed that the interaction of the GAP domain with Rop depended on the activation state of Rop; however, the CRIB domain interacted with both active and inactive forms of Rop. Rop complexes with aluminum tetraflouride mimic the transition state of Rop. They enhanced the interaction of CRIB and GAP domains with Rop, suggesting that both of these parts of RopGAP bind to the transition state of Rop.

Wu, G., Li, H., and Yang, Z. (2000) Arabidopsis RopGAPs are a novel family of Rho GTPase-activating proteins that require the Cdc42/Rac-interactive binding motif for Rop-specific GTPase stimulation. Plant Physiol. 124: 1625-1636. [Abstract] [Full Text]