Primary structure and functional expression of h-caldesmon complementary DNA.

Abstract Recently, the two Mr forms of caldesmon ( Mr ' s in the range of 120–150kDa and 70–80kDa as judged by SDS-PAGE) have been identified. h -Caldesmon (high Mr 120–150kDa caldesmon) is predominantly expressed in smooth muscles, and l-caldesmon (low Mr 70–80kDa caldesmon) in non-muscle cells. In this paper, we report the nucleotide sequence of chick embryo gizzard h -caldesmon cDNA and its translation into amino acid sequence. This sequence predicts a protein of 771 amino acids with a Mr of 88,743. The central portion of this sequence is composed of a 10-fold repeat of conserved amino acid sequence containing 13–15 amino acids. Further, a recombinant protein produced in Escherichia coli containing the full-length h -caldesmon cDNA has been characterized. Although the Mr of h -caldesmon predicted from amino acid sequence is 88,743, native and recombinant proteins show the same mol. wt. with 150kDa as measured by SDS-PAGE. This discrepancy may be due to the acidic amino acid-rich sequences at the N-terminal and central portions. A recombinant protein produced in E. coli possesses calmodulin-, F-actin- and tropomyosin-binding abilities in common with the native h -caldesmon.