title: Structural and functional organization of gizzard myosin molecules: proteolytic digestion and N-iodo-acetyl-N-(5-sulfo-1-naphthyl)ethylene diamine modification.
abstract: The proteolytic digestibility of gizzard myosin and the reactivity of its thiol groups were studied using three different proteases and I-AEDANS, respectively. The digestibility and reactivity were both observed to be specifically affected by the presence of ATP and the KCl concentration. It was thus indicated that the 22-Kd fragments produced by papain digestion participate in the ATP-induced change in molecular conformation of gizzard myosin. Evidence was also obtained that the 22-Kd fragments are a part of the myosin head and located adjacent to the myosin neck. Thiol groups of the 22-Kd fragments were shown to be of the SH1 type, that is, their modification by I-AEDANS resulted in inhibition of the EDTA-ATPase activity and activation of the Ca-ATPase activity. Moreover, blocking the SH1 groups of 22-Kd fragments, like phosphorylation of regulatory light chains, made myosin filaments resistant to the disassembling action of ATP, and caused the Mg-ATPase activity of actomyosin in the presence of NTM to become insensitive to calcium ions. The correlation between structural and functional organization of gizzard myosin molecules was revealed in some detail by these studies (Fig. 11B).
mesh_terms: D000251:Adenosine Triphosphatases / Q000378:metabolism; D000255:Adenosine Triphosphate / Q000378:metabolism; D000818:Animals; D002118:Calcium / Q000494:pharmacology; D000252:Calcium-Transporting ATPases / Q000378:metabolism; D002645:Chickens / Q000378:metabolism; D002918:Chymotrypsin; D004789:Enzyme Activation / Q000187:drug effects; D005895:Gizzard, Avian / Q000378:metabolism / Q000648:ultrastructure; D008970:Molecular Weight; D009218:Myosins / Q000378:metabolism*; D009282:Naphthalenesulfonates / Q000378:metabolism; D010206:Papain; D010455:Peptides / Q000032:analysis; D011189:Potassium Chloride / Q000378:metabolism; D011487:Protein Conformation; D013438:Sulfhydryl Compounds / Q000378:metabolism
chemical_list: D009282:Naphthalenesulfonates; D010455:Peptides; D013438:Sulfhydryl Compounds; D011189:Potassium Chloride; C006421:1,5-I-AEDANS; D000255:Adenosine Triphosphate; D002918:Chymotrypsin; D010206:Papain; D000251:Adenosine Triphosphatases; D009218:Myosins; D000252:Calcium-Transporting ATPases; D002118:Calcium