An amino acid sequence for a Chlamydamomass calmodulin has been elucidated with emphasis on the characterization of differences that are unique to Chlamydomomwa and Dicyostdlium calmodulin. While the concentration of calmodulin required for half-maximal activation of plant NAD kinase varies among vertebrate, higher plant, algal, and slime mold calmodulins, only calmodulins from the unicellular ala Chlamydomoxas and the slime mold Dictyostelium show increased maximal activation of NAD kinase (Roberts, Burgess, Watterson 1984 Plant Physiol 75: 796- 798; Marshak, Clarke, Roberts, Watterson 1984 Biochemistry 23: 2891- 2899). The same preparations of calmodulin do not show major differences in phosphodiesterase or myosin light chain kinase activator activity. We report here that a Chklmydomonas calmodulin has four primary structural features similar to Dictyosteliam that are not found in other calmodulins characterized to date: an altered carboxy terminus including a novel 11-residue extension for Chlamydomons calmodulin, unique residues at positions 81 and 118, and an unmethylated lysine at position 115. The only amino acid sequence identity unique to Chlamydomoxu and Dicyostefium calmodulin is the presence of a lysine at position 115 instead of a trimethyllysine. These studies indicate that the methylation state of lysine 115 may be important in the maximal NAD kinase activator activity of calmodulin and support the concept that calmodulin has multiple functional domains in addition to multiple structural domains.
ASJC Scopus subject areas
- Plant Science