Fate of the light chains in the course of proteolytic digestion of rabbit fast skeletal myosin.
During proteolytic digestion of myosin to prepare HMM or HMM-S-1 subfragments, myosin light chains are affected variously according to experimental conditions. In the presence of Ca2+ at low ionic strength trypsin rapidly degrades the DTNB light chain to a 18 K peptide. This new DTNB light chain is compared to a DTNB (17K) light chain obtained by chymotryptic digestion under similar conditions as shown here and in parallel studies. (Weeds and Pope (1977), J. Mol. Biol, 111, 129--157). Whereas the chymotryptic DTNB (17K) has lost its phosphorylation site (Ser-15), tryptic DTNB (18K) has lost only a strongly basic N-terminal peptide. A transitory (ca 14K) fragment is formed when digestion occurs in the presence of EDTA. A-1 light chain (20.7K) is cut to form a 20K species when myosin (of (CT)-HMM obtained ina high ionic strength medium) is digested with trypsin whether Me2+ is present or not. The new formed species has also lost its strongly basic N-terminal peptide and assumes a primary structure closer to that of A-2. Chymotrypsin was shown to have no effect on the A-1 light chain under the present conditions, whereas A-2 is not affected by chymotrypsin or trypsin under any of the conditions described in the present study.
D000818:Animals; D055598:Chemical Phenomena; D002621:Chemistry; D002918:Chymotrypsin; D004228:Dithionitrobenzoic Acid; D004492:Edetic Acid; D006868:Hydrolysis; D008970:Molecular Weight; D009218:Myosins; D009994:Osmolar Concentration; D010446:Peptide Fragments; D011817:Rabbits; D014357:Trypsin
D010446:Peptide Fragments; D004228:Dithionitrobenzoic Acid; D004492:Edetic Acid; D002918:Chymotrypsin; D014357:Trypsin; D009218:Myosins