超静定结构支座反力计算的单位支座位移法.pdf

超静定结构支座反力计算的单位支座位移法.PDFThe Minimal Autoinhibited Unit of the Guanine
Nucleotide Exchange Factor Intersectin
K. Farid Ahmad, Wendell A. Lim*
Department of Cellular and Molecular Pharmacology, University of California San Francisco, San Francisco, California, United States of America
Abstract
Intersectin-1L is a member of the Dbl homology (DH) domain guanine nucleotide exchange factors (GEF) which control Rho-
family GTPase signaling. Intersectin-1L is a GEF that is specific for Cdc42. It plays an important role in endocytosis, and is
regulated by several partners including the actin regulator N-WASP. Intact intersectin-1L shows low Cdc42 exchange
activity, although the isolated catalytic DH domain shows high activity. This finding suggests that the molecule is
autoinhibited. To investigate the mechanism of autoinhibition we have constructed a series of domain deletions. We find
that the five SH3 domains of intersectin are important for autoinhibition, with the fifth domain (SH3(E)) being sufficient for
the bulk of the autoinhibitory effect. This SH3 domain appears to primarily interact with the DH domain. We have
determined the crystal structure of the SH3(E)-DH domain construct, which shows a domain swapped arrangement in which
the SH3 from one monomer interacts with the DH domain of the other monomer. Analytical ultracentrifugation and gel
filtration, however, show that unde