A novel 190 kDa calmodulin-binding protein associated with brain actomyosin.

We present evidence for a novel calmodulin-binding protein associated with Ca2+-sensitive, non-muscle actomyosin from rabbit brain. Gel filtration chromatography of brain actomyosin and SDS-PAGE analysis of resulting fractions revealed the presence of a stable complex of a 190 kDa polypeptide and calmodulin. Furthermore, brain actomyosin was retained on a column of conjugated calmodulin-Sepharose 4B and eluted by 6 M urea in the presence of Ca2+. Further elution with 6M urea plus EGTA released the 190 kDa polypeptide from the column. These results show that the 190 kDa polypeptide forms a tight complex with calmodulin and that this complex associates with brain actomyosin in a Ca2+-independent manner.