Proteome analysis of whole and water-soluble proteins in masseter and semitendinosus muscles of Holstein cows.

To assess both quantitative and qualitative differences between the slow- and fast-type muscles, masseter (slow) and semitendinosus (fast) from four Holstein cows were analyzed by two-dimensional difference gel electrophoresis (2D DIGE) and mass spectrometry. The proteome analysis identified 27 spots as 20 proteins in the whole protein fraction extracted with 8 mol/L urea solution, and 16 spots were identified as 11 proteins in the water-soluble protein fraction. Two slow-type myofibrillar proteins (myosin light chain-1 slow-b and myosin light chain-2 slow), and aconitase-2 mitochondria were present at higher levels in the masseter muscle (P < 0.05). Four fast-type myofibrillar proteins (myosin light chain-1 fast, myosin light chain-2 fast, myosin light chain-3 fast and tropomyosin-1), and three enzymes of glycolytic pathway (enolase-3, aldolase-A and triosephosphate isomerase), were present at higher levels in the semitendinosus muscle (P < 0.05). Our proteome analysis showed that the composition of sarcoplasmic proteins as well as myofibrillar proteins was clearly different between slow- and fast-type muscles.