Primary mutations in calmodulin prevent activation of the Ca+ +-dependent Na+ channel in Paramecium

✍ Scribed by Kit-Yin Ling; Robin R. Preston; Robert Burns; John A. Kink; Yoshiro Saimi; Dr. Ching Kung

• Publisher: John Wiley and Sons
• Year: 1992
• Tongue: English
• Weight: 684 KB
• Volume: 12
• Category: Article
• ISSN: 0887-3585
• DOI: 10.1002/prot.340120408

✦ Synopsis

Abstract

Paramecium tetraurelia behavioral mutant cam^12^ displays a “fast‐2” behavioral phenotype: it fails to respond to Na^+^ stimuli. Electrophysiologically, it lacks a Ca^+ +^‐dependent Na^+^ current. Genetics and DNA sequencing showed the primary defect of cam^12^ to be in the calmodulin gene (Kink et al., 1990). To correlate calmodulin structure and function in Paramecium, we elucidated the primary structure of cam^12^ calmodulin. Peptide sequencing confirmed the two point mutations predicted by the DNA sequence: a glycine‐to‐glutamate substitution at position 40 and an aspartate‐to‐asparagine substitution at position 50. Our results further showed that lysine 13 and lysine 115 were methylated normally in cam^12^. It is likely that the electrophysiological abnormalities of cam^12^ are a direct reflection of the amino‐acid substitutions, as opposed to improper posttranslational modification.