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Evidence for the Binding of Calmodulin to Endogenous B‐50 (GAP‐43) in Native Synaptosomal Plasma Membranes
Author(s) -
Graan Pierre N. E.,
Oestreicher A. Beate,
Wit Marina,
Kroef Marian,
Schrama Louise H.,
Gispen Willem Hendrik
Publication year - 1990
Publication title -
journal of neurochemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.75
H-Index - 229
eISSN - 1471-4159
pISSN - 0022-3042
DOI - 10.1111/j.1471-4159.1990.tb05808.x
Subject(s) - calmodulin , membrane , growth cone , endogeny , blot , biochemistry , binding protein , chemistry , biology , microbiology and biotechnology , enzyme , gene , axon
The neuron‐specific protein B‐50 has been described as an atypical calmodulin (CaM) binding protein, because the purified protein has a higher affinity for CaM in the absence than in the presence of Ca 2+ . We have studied CaM binding to endogenous B‐50 in native synaptosomal plasma membranes (SPM) and growth cone membranes in order to assess the physiological relevance of the binding. To detect B‐50/CaM binding, we used the cross‐linker disuccimidyl suberate (DSS) to form a covalent B‐50/CaM complex, which is stable on SDS‐PAGE. Upon addition of DSS, purified B‐50 and calmodulin form a 70‐kDa complex in the absence but not in the presence of Ca 2+ . This complex can be detected by protein staining and on Western blots using anti‐B‐50 and anti‐CaM IgGs. DSS treatment of SPM or growth cone membranes with or without exogenous CaM results in the formation of a 70‐kDa B‐50/CAM complex detectable only in the absence of Ca 2+ with both antibodies. Our results strongly suggest that the binding of CaM to endogenous B‐50 in SPM and growth cone membranes is of physiological relevance. CaM binding to B‐50 may be an important factor in regulating neurite outgrowth and/or neurotransmitter release.