title: Urea tolerance of myofibrillar proteins of two elasmobranchs: Squalus acanthias and Raja tengu.
abstract: Some biochemical properties of actomyosin and myosin from elasmobranchs, Squalus acanthias and Raja tengu are compared with those of a freshwater (Cyprinus carpio) and a marine teleost (Seriola quinquiradiata). Whereas Ca2+-ATPase of teleost actomyosins are more stable in the absence of urea, the reverse is true for elasmobranchs up to 1.0 M urea. In contrast to that of teleosts, the Mg2+-ATPase of S. acanthias actomyosin shows an activation in the presence of urea, where as that of R. tengu persists. Below 1.0 M urea, there is low incorporation of DTNB into thiols of elasmobranch myosins, and losses in alpha-helicity are reversible up to 5.0 M urea. The results, thus, demonstrate that for a certain concentration of urea, elasmobranch myofibrillar proteins may exhibit a group specific tolerance to urea.
mesh_terms: D000205:Actomyosin / Q000502:physiology*; D000222:Adaptation, Physiological; D000818:Animals; D017301:Ca(2+) Mg(2+)-ATPase / Q000378:metabolism; D000252:Calcium-Transporting ATPases / Q000378:metabolism; D004228:Dithionitrobenzoic Acid / Q000378:metabolism; D004284:Dogfish / Q000502:physiology*; D004555:Electric Fish / Q000502:physiology*; D009218:Myosins / Q000502:physiology*; D011487:Protein Conformation; D012754:Sharks / Q000502:physiology*; D012860:Skates, Fish / Q000502:physiology*; D014508:Urea / Q000494:pharmacology*
chemical_list: D014508:Urea; D000205:Actomyosin; D004228:Dithionitrobenzoic Acid; D017301:Ca(2+) Mg(2+)-ATPase; D009218:Myosins; D000252:Calcium-Transporting ATPases