A ubiquityl-calmodulin synthetase that effectively recognizes the Ca(2+)-free form of calmodulin

• Published in: FEBS letters Vol. 315; no. 3; pp. 347 - 352
• Main Authors: Majetschak, M, Laub, M, Jennissen, H P
• Format: Journal Article
• Language: English
• Published: England 11.01.1993
• Subjects: Animals; Autoradiography; Calcium - metabolism; Calmodulin - metabolism; Chromatography, Gel; Peptide Synthases - metabolism; Rabbits; Reticulocytes - enzymology; Substrate Specificity; Ubiquitin-Activating Enzymes; Ubiquitin-Protein Ligases
• ISSN: 0014-5793; 1873-3468
• DOI: 10.1016/0014-5793(93)81192-3

Ubiquityl-calmodulin synthetase (uCaM-synthetase) activity as detected in reticulocyte lysate and the crude extracts of rabbit tissues [FEBS Lett. 294 (1991) 229-233] has been well characterized as being essentially Ca(2+)-dependent (-Ca2+/+Ca2+ activity ratio: 0.15-0.2). However, during the purification of this enzyme on ubiquitin-Sepharose the Ca(2+)-dependent activity is lost and an essentially Ca(2+)-independent enzyme (-Ca2+/+Ca2+ activity ratio: 1.0-1.5) is obtained which was purified 90-fold (uCaM-Syn F1) to a final specific activity of 0.32 pkat/mg. During the purification procedure a second protein factor (uCaM-Syn F2) was isolated that has no catalytic activity by itself but restores Ca2+ dependence to the uCaM-Syn F1 fraction (-Ca2+/+Ca2+ activity ratio: 0.1) and enhances the catalytic activity in uCaM-Syn F1 in the presence of Ca2+ over 40-fold. It is concluded that several (possibly interdependent) forms of uCaM-synthetase exist which display different substrate specificities for calmodulin.