Interaction of two brain annexins, CaBP33 and CaBP37, with membrane-skeleton proteins

Abstract

CaPB33 and CaPB37, two annexins purified from bovine brain, interact with a Triton X-100-resistant fraction (cytoskeleton) from bovine brain membranes in a Ca 2+-dependent way in vitro. The binding is saturable with respect to the CaBP33–CaBP37 concentration, half-maximal binding occurring at ~15 μg of the CaBP33–CaBP37 mixture/ml. The binding of these two annexins to the crude cytoskeleton preparation as a function of free Ca 2+ concentration is biphasic, with half-maximal binding at ~ 50 μM and ~ 400 μM free Ca 2+ for the first and the second component, respectively. By an overlay technique, CaBP33 and CaBP37 bind to a set of low M r polypeptides (10–20 kDa) in the crude cytoskeleton preparation, with formation of an 85–90 kDa complex as investigated in cross-linking experiments. No binding of the CaBP33–CaBP37 mixture to either G-or F-actin has been observed. Identification of the CaBP33–CaBP37-binding proteins in cytoskeletons would help elucidating the function(s) of these annexins in the brain.