TAILIEUCHUNG - Báo cáo khoa học: A vertebrate slow skeletal muscle actin isoform

Salmonids utilize a unique, class II isoactin in slow skeletal muscle. This actin contains 12 replacements when compared with those from salmonid fast skeletal muscle, salmonid cardiac muscle and rabbit skeletal muscle. Substitutions are confined to subdomains 1 and 3, and most occur after residue 100. Depending on the pairing, the ‘fast’, ‘cardiac’ and rabbit actins share four, or fewer, substitutions. | ễFEBS Journal A vertebrate slow skeletal muscle actin isoform Wasana A. K. A. Mudalige Donna M. Jackman Deena M. Waddleton and David H. Heeley Department of Biochemistry Memorial university of Newfoundland St John s Canada Keywords actin muscle plasticity protein isoforms salmonid fishes slow skeletalmuscle Correspondence D. Heeley Department of Biochemistry MemorialUniversity of Newfoundland St. John s Newfoundland A1B 3X9 Canada Fax 1 709 737 2422 E-mail heeleydavid@ Database The novel amino acid sequences published here are available under the accession numbers AF304406 Atlantic salmon fast skeletal muscle actin AF267496 brown trout slow skeletalmuscle actin and AF303985 brown trout cardiac muscle actin Received 4 March 2007 revised 5 May 2007 accepted 11 May 2007 doi Salmonids utilize a unique class II isoactin in slow skeletal muscle. This actin contains 12 replacements when compared with those from salmonid fast skeletal muscle salmonid cardiac muscle and rabbit skeletal muscle. Substitutions are confined to subdomains 1 and 3 and most occur after residue 100. Depending on the pairing the fast cardiac and rabbit actins share four or fewer substitutions. The two salmonid skeletal actins differ nonconservatively at six positions residues 103 155 278 281 310 and 360 the latter involving a change in charge. The heterogeneity has altered the biochemical properties of the molecule. Slow skeletal muscle actin can be distinguished on the basis of mass hydroxylamine cleavage and electrophoretic mobility at alkaline pH in the presence of 8 M urea. Further compared with its counterpart in fast muscle slow muscle actin displays lower activation of myosin in the presence of regulatory proteins and weakened affinity for nucleotide. It is also less resistant to urea- and heat-induced denaturation. The midpoints of the change in far-UV ellipticity of G-actin versus temperature are 45 C slow actin and 56 C fast actin . Similar melting

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