Crude yeast ubiquitin-calmodulin ligase (uCaM-synthetase; EC 188.8.131.52) conjugated ubiquitin Ca(2+)-dependently to yeast and bovine calmodulin. Yeast calmodulin was also a substrate for uCaM-synthetase from rabbit reticulocytes.
Experiments with methylated ubiquitin in the heterologous reticulocyte system indicate that, as with vertebrate calmodulins, only one lysine residue of yeast calmodulin reacts with ubiquitin so that the incorporation of multiple ubiquitin molecules will lead to a polyubiquitin chain.
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Parag HA, Dimitrovsky D, Raboy B, Kulka RG. Selective ubiquitination of calmodulin by UBC4 and a putative ubiquitin protein ligase (E3) from Saccharomyces cerevisiae. FEBS Lett. 1993, 325:242-246.