Interaction of paratropomyosin with beta-connectin and its 400-kilodalton fragment from chicken skeletal muscle as influenced by the calcium ion concentration.
The binding of paratropomyosin to beta-connectin, which has been suggested to interact at the A-I junction of a sarcomere, was confirmed by measuring the changes in turbidity of a mixture with changing NaCl concentration, pH and free calcium ions, and by morphological observation and a coprecipitation assay of the aggregates formed in the mixture. Paratropomyosin also bound to the 400-kDa fragment which is the N-terminal portion of beta-connectin and contains the A-I junction region. Moreover, the interaction of paratropomyosin with the 400-kDa fragment was enhanced by a calcium ion concentration from 10(-7) M to 10(-5) M and markedly suppressed above 10(-4) M calcium ions. We conclude that paratropomyosin probably binds to the 400-kDa fragment of beta-connectin in the A-I junction region in living and pre-rigor skeletal muscle. In postmortem skeletal muscle paratropomyosin may be released from the 400-kDa portion of the connectin filament by increased calcium ion concentration and translocated on to thin filaments to induce meat tenderization.
Fei
S
S
Graduate School of Science and Technology, Faculty of Agriculture, Kobe University, Japan.
Yamanoue
M
M
Okayama
T
T
D000818:Animals; D002118:Calcium / Q000032:analysis*; D002645:Chickens; D064211:Connectin; D008567:Membranes, Artificial; D008970:Molecular Weight; D009124:Muscle Proteins / Q000737:chemistry*; D018482:Muscle, Skeletal / Q000737:chemistry*; D009391:Nephelometry and Turbidimetry; D010446:Peptide Fragments / Q000737:chemistry*; D011485:Protein Binding; D011494:Protein Kinases / Q000737:chemistry*; D014335:Tropomyosin / Q000737:chemistry*
D064211:Connectin; D008567:Membranes, Artificial; D009124:Muscle Proteins; D010446:Peptide Fragments; D014335:Tropomyosin; D011494:Protein Kinases; D002118:Calcium