Skeletal muscle calcium channel ryanodine binding activity in genetically unimproved and commercial turkey populations
1999
Wang, L.J. | Byrem, T.M. | Zarosley, J. | Booren, A.M. | Strasburg, G.M.
The biochemical basis for the incidence of pale, soft, exudative (PSE) turkey meat was investigated by conducting ryanodine binding experiments on sarcoplasmic reticulum (SR) vesicles prepared from genetically unimproved and commercial turkeys. Ryanodine binding to the Ca(2+) channel protein in SR vesicles from both populations of turkeys was activated at a threshold concentration of approximately 0.2 micromol Ca(2+), reached a plateau over the range of 3 to 30 micromol free Ca(2+), and was only slightly inhibited at 1 mM Ca(2+). The SR fractions, enriched in the Ca(2+)-channel protein, from commercial turkeys exhibited a higher (P < 0.05) mean affinity for ryanodine when compared to that from unimproved turkeys (K(d) = 12.2 vs 20.5 nM, respectively). A fourfold difference (P < 0.05) in mean Ca(2+)-channel protein content or B(max) (1.10 pmol/mg vs 4.01 pmol/mg) was observed between commercial and unimproved turkey SR fractions. The apparent difference in channel protein content between the two populations may be partially accounted for by the high abundance of a 75-kDa protein, as yet unidentified, observed in most commercial turkey samples on SDS polyacrylamide gels. The differences in ryanodine binding activity between these two populations of turkeys suggest that altered SR calcium channel protein activity, or altered channel regulation, may be associated with the increased incidence of PSE meat from turkeys selected for growth characteristics.
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