Ubiquitin-calmodulin ligase (uCaM synthetase: EC 18.104.22.168) holosystem can be separated into two essential protein components: uCaM Syn-F1, a ubiquitin-binding protein belonging to the ubiquitin-activating enzyme family (E1)  and uCaM Syn-F2 which bestows the reaction specificity leading to the covalent modification of calmodulin with ubiquitin . A novel type of substrate recognition ("global recognition") allowing the existence of compensatory catalytic recognition sites in a calmodulin molecule is suggested based on alternative ubiquitylation of K13 or K94 instead of K21 .
Multiubiquitylation strongly decreases the biological activity of calmodulin towards phosphorylase kinase by reducing its affinity approximately threefold and the maximal degree of activation approximately twofold 
Laub M, Steppuhn JA, Bluggel M, Immler D, Meyer HE, Jennissen HP
Modulation of calmodulin function by ubiquitin-calmodulin ligase and identification of the responsible ubiquitylation site in vertebrate calmodulin. Eur.J Biochem 1998, 255:422-431. 
Majetschak M, Laub M, Meyer HE, Jennissen HP The ubiquityl-calmodulin synthetase system from rabbit reticulocytes: isolation of the ubiquitin-binding first component, a ubiquitin-activating enzyme. Eur.J Biochem 1998, 255:482-491. 
Majetschak M, Laub M, Klocke C, Steppuhn JA, Jennissen HP:
The ubiquityl-calmodulin synthetase system from rabbit reticulocytes: isolation of the calmodulin-binding second component and enzymatic properties. Eur.J.Biochem. 1998, 255:492-500. 
Laub M, Rumpf H, Jennissen HP: Analysis of substrate specificity of ubiquitin-calmodulin ligase: biochemical versus molecular biology approach. Biological Chemistry 2000, 381:S255.