A C-terminal, calmodulin-like regulatory domain from the plasma membrane Ca2"-pumping ATPase (inhibitory domain/immunochromogenic screening/sarcoplasmic reticulum Ca2+-ATPase)

Le résumé fourni par la source

A cDNA that encodes what appears to be the inhibitory domain of the plasma membrane calcium-pumping ATPase (Ca2-ATPase) has been isolated by screening a Agtll bovine brain cDNA library with antibodies prepared against the human erythrocyte membrane Ca2 -ATPase. This screen- ing resulted in isolation of a bacteriophage containing a 1.5-kilobase cDNA insert encoding a 71-residue polypeptide, the remainder being a large 3' terminal noncoding region. A portion of this deduced peptide sequence was identical to that of a peptide isolated from a V8 protease digest of the human erythrocyte Ca2 + -ATPase except for 1 residue. Antibodies purified by immunoabsorption to the fusion protein containing this cDNA-encoded polypeptide reacted only with those frag- ments of a limited trypsin digest of the human erythrocyte Ca2+ -ATPase that contain the inhibitory domain. Moreover, these antibodies were able to partially stimulate basal enzyme activity and block further activation by calmodulin. The en- coded polypeptide bears homology to the glutamic acid-rich regions N-terminal to the Ca2 + -binding loops of calmodulin and to a lesser extent with the loops themselves. This encoded polypeptide also represents the C terminus of the Ca2 - ATPase. Portions of the isolated cDNA were homologous to the 3' noncoding region of the sarcoplasmic reticulum Ca2+- ATPase cDNA, indicating a possible mechanism for the evolu- tion of these distinct membrane Ca2 + pumps.

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