Peptide mapping of polymorphic myosin heavy chain isoforms in different muscle types of some freshwater teleosts

Abstract

A modified SDS-PAGE system has been employed to resolve polymorphic myosin heavy chain (MyHC) isoforms in different muscle types of three freshwater teleosts displaying different modes of respiration, adaptive features and life styles. Investigated species include accessory air-breather Channa punctata along with exclusive aquatic breather major carps Labeo rohita and Catla catla. All the selected species show specificity and expressivity of at least three MyHC isoforms, one each in red, head and pectoral muscles. Chymotryptic peptide maps unambiguously support substructural individuality of each MyHC isoforms with the type-specific dispersal of chymotryptic cleavage sites. Specific Ca(2+)- and Mg(2+)-ATPase activities of natural actomyosin (NAM) of lateral line red muscle of C. punctata were low and less sensitive to pH, but sensitive to KCl concentrations between 0.05 and 0.15M. In comparison, the specific enzymatic activities of NAM of red muscle from the carps (L. rohita and C. catla) were substantially high with prominent peaks at pH 7.5 and near insensitivity to 0.05-0.15M KCl, while C. punctata had shown a different response at these molarities. Thus, the data favor a correlation between breathing modes and life style and the differences in pH or ionic strength sensitivities of ATPases. Unique profiles of peptide maps and the dispersal patterns of hydrophobic residues (cleavage sites of chymotrypsin) in MyHC of different muscle types further reflect individuality of their evolutionary histories.