%D 1994
%O Thesis digitised by ProQuest.
%X n-chimaerin is a GAP for the ras-related p21rac. A 45 kDa brain protein
(p45) immune reactive to anti-n-chimaerin polyclonal antibodies had selective
p21 rac GAP activity, using an overlay assay. p45-chimaerin was purified 400-
fold from rat brain by column chromatography. Tryptic peptides contained
sequences identical to that predicted from α2-chimaerin cDNA, a splice variant
encoding a divergent N-terminal with a SH2 domain. Thus, p45-chimaerin
probably corresponds to SH2-containing (α2) chimaerin. A 35 kDa p21rac GAP
(p35) detected in detergent soluble membrane fractions, immunoreactive to
chimaerin antiserum was likely to represent n-chimaerin (α1-chimaerin). Diverse
GAPs for the rho/rac family were present in the brain; p45-chimaerin was widely
distributed in brain regions except cerebellum, and was present in both
membrane and cytosolic fractions.
Both native and recombinant a2-chimaerin exhibited p21rac GAP activity
in solution, which was stimulated by phosphatidylserine with a synergistic effect
by phorbol esters. GAP activity of α2-chimaerin was unaffected by its SH2
domain. In contrast to α1-chimaerin, α2-chimaerin bound more phorbol ester
in the presence of phosphatidylinositol than of phosphatidylserine. α2-Chimaerin
was phosphorylated by PKC and PKA in vitro. Brain proteins interacting with
α2-chimaerin were detected using 32P-labelled PKC phosphorylated chimaerin.
A 60 kDa protein interacting with the SH2 domain of α2-chimaerin was purified;
peptide sequences showed it to be novel. Two peptides had similarity to the
consensus sequences of a MAP kinase substrate and a SH2 binding domain.
These data suggest that α2-chimaerin plays a physiological role in neuronal
signal transduction involving SH2-linked receptor/tyrosine kinase and p21rac
signalling pathways.
%L discovery10098872
%T Purification and functional characterization of brain and recombinant chimaerin, a p21rac GTPase activating protein
%A Mabel Teo
%I UCL (University College London)