Open AccessBiochemical and theoretical approach to localization of metal‐ion‐binding sites in the actin primary structure
Author(s) -
STRZELECKAGOŁLASZEWSKA Hanna,
BOGUTA Grzegorz,
ZMORZYŃSKI Stainslaw,
MORACZEWSKA Joanna
Publication year - 1989
Publication title -
european journal of biochemistry
Language(s) - English
Resource type - Journals
eISSN - 1432-1033
pISSN - 0014-2956
DOI - 10.1111/j.1432-1033.1989.tb14830.x
Subject(s) - actina , divalent , actin , skeletal muscle , binding site , actin binding protein , chemistry , biophysics , gene isoform , biochemistry , gizzard , crystallography , cytoskeleton , biology , actin cytoskeleton , anatomy , cell , paleontology , organic chemistry , gene
The number of Ca 2+ ions bound at sites other than the single high‐affinity site in CaCl 2 ‐induced polymers of rabbit skeletal muscle, chicken gizzard, and bovine aorta actin was determined. The polymer of skeletal muscle and aorta actin contained 4 mol Ca 2+ /mol, whereas gizzard actin only 3 mol weakly bound Ca 2+ /mol monomer. This difference correlates with the deletion in smooth muscle γ‐actin of one out of four NH 2 ‐terminal acidic residues typical of skeletal and smooth muscle α‐actin isoforms, suggesting that this additional acidic residue in α‐actins is involved in the weak binding of cations which is essential for polymerization. This experimental result, as well as a theoretical analysis of the actin primary structure, argue against the implication of the NH 2 ‐terminal acidic residues in the high‐affinity site for divalent cation. The analysis of the actin primary structure aimed at identification of sequences resembling the known Ca 2+ ‐binding patterns has revealed the absence of an EF‐hand Ca 2+ ‐binding site. The best match was obtained between the sequence of the 292–301/segment and that of Ca 2+ site in lectins. However, in the light of experimental data discussed, it is more plausible that the actual high‐affinity Ca 2+ site in actin involves sequentially distant residues from the NH 2 ‐ and COOH‐terminal portions of the polypeptide chain.