Post-mortem changes in cytoskeletal proteins of muscle

Area of Science:

• Meat science
• Protein biochemistry
• Muscle biology

Background:

• Muscle ageing involves progressive changes in protein solubility.
• Cytoskeletal proteins, specifically desmin and connectin, are key in muscle structure.
• Understanding these changes is crucial for meat quality.

Purpose of the Study:

• To investigate post-mortem changes in muscle cytoskeletal protein solubility.
• To identify specific proteins affected during muscle ageing.
• To correlate protein changes with meat properties like tenderness.

Main Methods:

• Ox sternomandibularis muscle samples collected post-mortem up to six days.
• Homogenization and separation into phosphate, KI, and guanidine-HCl soluble fractions.
• Protein analysis using sodium dodecylsulphate polyacrylamide gel electrophoresis (SDS-PAGE).

Main Results:

• Confirmed previously reported changes in protein solubility.
• Observed disappearance of desmin (guanidine fraction) due to proteolysis.
• Noted partial loss of connectin from the guanidine fraction, with a new 110,000 D polypeptide appearing.
• Desmin's in vivo role as Z-disc linked collars identified; its loss correlates with myofibril disintegration.

Conclusions:

• Loss of desmin during post-mortem storage contributes to muscle disintegration into myofibrils.
• Cytoskeletal network breakdown explains post-mortem changes in meat physical properties and increased tenderness.
• Cold shortening does not influence these specific protein solubility changes or gel patterns.