title: Specific interactions of the alkali light chain 1 in skeletal myosin heads probed by chemical cross-linking.
abstract: We have investigated the enzymatic properties of the 120K cross-linked heavy-chain-light-chain derivative formed upon reaction of chymotryptic myosin subfragment 1 (S-1) isoenzymes with the bis(imido esters) dimethyl 3,3'-dithiobis(propionimidate) and dimethyl suberimidate. The formation of the 120K product was accompanied for S-1(A1) but not for S-1(A2) by a loss of the actin-activated ATPase without alteration of the Ca2+-ATPase whereas the Mg2+-ATPase was increased 2-fold. Up to 70%, the inhibition of the acto-S-1(A1) ATPase activity was closely correlated with the extent of cross-linking of the A1 light chain; this activity could be largely restored upon cleavage of the cross-link using the reversible cross-linker dimethyl 3,3'-dithiobis(propionimidate). The covalent link affected the acto-S-1(A1) Mg2+-ATPase activity by reducing 3-fold the Vmax and increasing 2-fold the Kapp. On reacting for the first time the hydrophobic, carboxyl group directed cross-linker N-ethoxycarbonyl-2-ethoxy-1,2-dihydroquinoline (EEDQ) with the acto-S-1(A1 + A2) complex, we found that the N-terminal tail of the A1 light chain was cross-linked to actin to an extent much larger than observed earlier with the water-soluble 1-ethyl-3-[3-(dimethylamino)propyl]carbodiimide; like the latter agent, EEDQ elicited the covalent union of the A1 subunit to the COOH-terminal part of actin. This cross-linker appears to be a valuable chemical probe of the F-actin-A1 light-chain interaction.(ABSTRACT TRUNCATED AT 250 WORDS)
mesh_terms: D000199:Actins / Q000378:metabolism; D000251:Adenosine Triphosphatases / Q000378:metabolism*; D000818:Animals; D017301:Ca(2+) Mg(2+)-ATPase / Q000378:metabolism; D000252:Calcium-Transporting ATPases / Q000378:metabolism; D002918:Chymotrypsin; D003432:Cross-Linking Reagents / Q000494:pharmacology*; D007527:Isoenzymes / Q000378:metabolism*; D007700:Kinetics; D008970:Molecular Weight; D009132:Muscles / Q000201:enzymology; D015879:Myosin Subfragments; D009218:Myosins / Q000378:metabolism*; D010446:Peptide Fragments / Q000378:metabolism*; D011817:Rabbits
chemical_list: D000199:Actins; D003432:Cross-Linking Reagents; D007527:Isoenzymes; D015879:Myosin Subfragments; D010446:Peptide Fragments; D002918:Chymotrypsin; D000251:Adenosine Triphosphatases; D017301:Ca(2+) Mg(2+)-ATPase; D009218:Myosins; D000252:Calcium-Transporting ATPases