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Crosslinking of trypsin digested acto‐heavy meromyosin as a probe of the affinity of the two myosin heads to actin
Author(s) -
Pliszka Barbara
Publication year - 1987
Publication title -
febs letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.593
H-Index - 257
eISSN - 1873-3468
pISSN - 0014-5793
DOI - 10.1016/0014-5793(87)81355-8
Subject(s) - heavy meromyosin , myosin , actin , myosin head , trypsin , biochemistry , chemistry , proteolysis , digestion (alchemy) , nucleotide , biophysics , biology , chromatography , enzyme , myosin light chain kinase , gene
The interaction of the two heads of the myosin molecule with actin was studied by tryptic digestion of HMM in the presence of actin, followed by crosslinking the two nicked heavy chains with Nbs 2 at the S2 region. In view of the protection by actin of thekDa junction against proteolysis, the percentage of the heads interacting with actin was estimated from the proportion of the 110 kDa to the 60 kDa digestion product. Under conditions such that about 50% of HMM heads were protected by actin (at an actin to HMM head molar ratio of 1:1 in the absence of nucleotide, or 3:1 in the presence of 5 mM ADP), the crosslinking of the digestion products yielded a 230 kDa (110+110 kDa), 125 kDa (60+60 kDa) and 175 kDa (60+110 kDa) species. Since the latter should be the only crosslinking product when only one head of HMM molecule is protected by actin, it is concluded that there is no preferential binding of one of the two HMM heads to actin in the presence of ADP or at equimolar actin to myosin heads ratio.