Mohammad A. Ilian (a), Roy Bickerstaffe (a) and Marion L. Greaser, , (b)
Meat Science, 2004, 66: 231-240
Abstract
An immunofluorescence microscopy method for following changes in myofibrillar-bound calpain 3 was developed. Afterward, proteolytic changes in calpain 3(p94), calpain 1, titin, and nebulin were examined in myofibrils prepared from ovine longissimus thoracis et lumborum (LTL) stored for 0, 1, 2, and 3 days postmortem. Western blot analysis revealed that the levels of intact calpain 3 (expressed as percentage of the level immediately postmortem) were 80%, 10% and not detectable in myofibrils prepared at 1, 2, and 3 days, respectively. Western blots for calpain 1 also indicated conversion of the intact protein (80 kDa) to a 76 kDa fragment during the same time period. Thus calpains 1 and 3 appear to be activated during postmortem storage. Immunofluorescence microscopy using an IS1 region specific antibody revealed that calpain 3 staining was most intense at the sarcomere Z- and M-lines. The fluorescence intensity declined significantly during storage, paralleling changes in the proteolytic breakdown of titin and nebulin associated with these structures.
Author Keywords: Skeletal muscle; Titin; Nebulin; Calpain; Tenderness
Corresponding author. Tel.: +1-608-262-1456; fax: +1-608-265-3110
(a) Molecular Biotechnology Group, Animal and Food Sciences Division, PO Box 84, Lincoln University, Canterbury, New Zealand
(b) Muscle Biology Laboratory, University of Wisconsin-Madison, Madison, WI 53706, USA | 
