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A Ca 2+ ‐Dependent Protein Kinase Activity Associated with Serotonin Binding Protein
Author(s) -
Adlersberg Mella,
Liu KuoPeing,
Hsiung ShuChi,
Ehrlich Yigal,
Tamir Hadassah
Publication year - 1987
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.1471-4159.1987.tb10000.x
Subject(s) - mitogen activated protein kinase kinase , autophosphorylation , map2k7 , protein kinase c , protein kinase a , cyclin dependent kinase 2 , casein kinase 2, alpha 1 , cgmp dependent protein kinase , cyclin dependent kinase 9 , chemistry , casein kinase 1 , casein kinase 2 , biochemistry , map kinase kinase kinase , ask1 , c raf , synapsin i , kinase , vesicle , membrane , synaptic vesicle
The endogenous phosphorylation of serotonin binding protein (SBP), a soluble protein found in central and peripheral serotonergic neurons, inhibits the binding of 5‐hydroxytryptamine (5‐HT, serotonin). A protein kinase activity that copurifies with SBP (SBP‐kinase) was partially characterized and compared with calcium/calmodulin‐dependent protein kinase II (CAM‐PK II). SBP itself is not the enzyme since heating destroyed the protein kinase activity without affecting the capacity of the protein to bind [ 3 H]5‐HT. SBP‐kinase and CAM‐PK II kinase shared the following characteristics: (1) size of the subunits; (2) autophosphorylation in a Ca 2+ ‐dependent manner; and (3) affinity for Ca 2+ . In addition, both forms of protein kinase phosphorylated microtubule‐associated proteins well and did not phosphorylate myosin, phosphorylase b., and casein. Phorbol esters or diacylglycerol had no effect on either of the protein kinases. However, substantial differences between SBP‐kinase and CAM‐PK II were observed: (1) CAM enhanced CAM‐PK II activity, but had no effect on SBP‐kinase; (2) synapsin I was an excellent substrate for CAM‐PK II, but not for SBP‐kinase; (3) 5‐HT inhibited both the autophosphorylation of SBP‐kinase and the phosphorylation of SBP, but had no effect on CAM‐PK II. These data indicate that SBP‐kinase is different from CAM‐PK II. Phosphopeptide maps of SBP and SBP‐kinase generated by digestion with S. aureus V 8 protease are consistent with the conclusion that these proteins are distinct molecular entities. It is suggested that phosphorylation of SBP may regulate the transport of 5‐HT within neurons.