Slow skeletal muscle actin: confirmation and further insights

• Main Author: Mercer, Robert C. C.
• Format: Thesis
• Language: English
• Published: Memorial University of Newfoundland 2010
• Subjects: Atlantic salmon; Salmo salar
• Online Access: https://research.library.mun.ca/8929/; https://research.library.mun.ca/8929/1/Mercer_RobertCC.pdf

1) The 1° structures of three sarcomeric actin isoforms were inferred from cDNA sequences: Atlantic herring (Clupea harengus) fast skeletal muscle actin, Acc# GQ455648; Atlantic herring slow skeletal muscle actin, Acc# EF495203; and Atlantic Mackerel (Scomber scombrus) fast skeletal muscle actin, Acc# EF607093. The two herring skeletal muscle actin cDNAs possess different non-coding regions and are concluded to arise from different genes. -- 2) Sequence comparisons demonstrate that actin from a given type of skeletal muscle has been conserved across teleost evolution. Herring slow muscle actin and salmonid slow muscle actin (Salmo trutta; Acc# AF267426 [Mudalige et.al. 2007]) share a single substitution, Gin 354 Ala (herr:sal), while, in addition to this substitution the fast skeletal muscle actins from Atlantic herring and atlantic salmon (Salmo salar; Acc# AF304406 [Mudalige et.al. 2007]) contain Ser 160 Thr for a total of two substitutions. -- 3) There are thirteen inferred substitutions between fast and slow skeletal muscle actins isolated from Atlantic herring, six that are non-conservative in nature. This is a record for two vertebrate sarcomeric actins. The replacements (non-conservative underlined) are: residues: 2, 3, 103, 155, 160, 165, 278, 281, 310, 329, 358, 360 and 363. Most of the heterogeneity occurs after residue 100. Also of note is the exchange of Gin (fast actin) for Asp (slow actin) at position 360, which endows the slow type isoform with a greater negative charge in the neutral pH range. Comparison with the actin found in the skeletal muscles of the rabbit demonstrates 11 replacements (five non-conservative) with herring slow skeletal muscle actin and four (one non-conservative) when compared to herring fast skeletal muscle. -- 4) Two skeletal muscle actins of non-identical net-charge were detected by alkaline urea PAGE in the slow skeletal muscle of the following species - mackerel and smelt - but not in other teleosts (halibut and tiliapia), primitive fish (hagfish and lamprey), birds or ...