Oligomerization of mouse alpha 1-syntrophin and self-association of its pleckstrin homology domain 1 containing sequences

Syntrophins are known to self-associate to form oligomers. Mouse alpha 1-syntrophin sequences were produced as chimeric fusion proteins in bacteria and were found to also oligomerize and in a micromolar Ca(2+)-dependent manner. The oligomerization was localized to the N-terminal pleckstrin homology domain (PH1) or adjacent sequences; the second, C-terminal PH2 domain did not show oligomerization. PH1 was found to self-associate, and calmodulin or Ca(2+)-chelating agents such as ethylene glycol bis(beta-aminoethyl ether)-N,N,N',N'-tetraacetic acid (EGTA) could effectively prevent this oligomerization. A single calmodulin bound per syntrophin to cause inhibition of the precipitation. Since calmodulin inhibited syntrophin oligomerization in the presence or absence of Ca(2+), Ca(2+) binding to syntrophin is responsible for the inhibition by EGTA of syntrophin oligomerization.