Connectin content and its post-mortem changes in fish muscle.

Connectin was isolated from fish dorsal myofibrils by an SDS-gel filtration method and estimated to account for approximately 13% of the total myofibrillar proteins. There was no significant difference in the amount of connectin among seven fish species but rabbit skeletal myofibrils contained a slightly higher content (16%) of connectin. The high molecular weight connectins from carp and rabbit both showed a doublet band, consisting of bands 1 and 2, on SDS-polyacrylamide gel electrophoresis using a large-pore gel. However, rabbit band 1 (a component of the connectin doublet) was found to migrate more slowly than carp band 1. During post-mortem ageing of the muscles, it was observed that the band 1 component rapidly disappeared with a concomitant increase in band 2 component and then the band 2 component was transformed slowly into faster migrating components. These results suggest that post-mortem ageing has qualitatively similar effects on the submolecular compositions of carp and rabbit connectins. However, the apparent rate of disappearance of the band 1 component was considerably higher in carp muscle than that in rabbit muscle.