A calmodulin-like protein in the bacterial genus Streptomyces.
The gene, named cabB, encoding a calmodulin-like protein of 70 amino acids containing two helix-loop-helix EF-hand motifs was cloned from Streptomyces coelicolor A3(2). cabB was transcribed from a single promoter throughout growth. The CabB protein produced in Escherichia coli was a monomer in solution, although it corresponded to one half of a dumbbell shape of the eukaryotic calmodulins. CabB bound calcium and upon binding of calcium its alpha-helix content was increased, as determined by circular dichroism spectroscopy. The growth of cabB-disruptants (mutant DeltacabB) on minimal agar medium containing calcium higher than 20 mM was delayed, suggesting that CabB has a role in calcium homeostasis by serving as a calcium buffer or transporter, as suggested for calerythrin in actinomycetes and the invertebrate sarcoplasmic calcium-binding proteins. Wide distribution of cabB almost exclusively in actinomycetes suggests a common role of EF-hand CabB-type proteins in these filamentous, soil-dwelling Gram-positive bacterial genera.
Yonekawa
Tohru
T
Department of Biotechnology, Graduate School of Agriculture and Life Sciences, The University of Tokyo, Bunkyo-ku, Tokyo 113-8657, Japan.
Ohnishi
Yasuo
Y
Horinouchi
Sueharu
S
D002118:Calcium / Q000378:metabolism*; D002135:Calcium-Binding Proteins / Q000235:genetics*; D002147:Calmodulin / Q000032:analysis* / Q000235:genetics; D003001:Cloning, Molecular; D020832:EF Hand Motifs; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism; D013302:Streptomyces / Q000378:metabolism*
D002135:Calcium-Binding Proteins; D002147:Calmodulin; D002118:Calcium