Differences in Beef Quality between Angus (Bos taurus taurus) and Nellore (Bos taurus indicus) Cattle through a Proteomic and Phosphoproteomic Approach

Abstract

Proteins are the major constituents of muscle and are key molecules regulating the metabolic changes during conversion of muscle to meat. Brazil is one of the largest exporters of beef and most Brazilian cattle are composed by zebu (Nellore) genotype. Bos indicus beef is generally leaner and tougher than Bos taurus such as Angus. The aim of this study was to compare the muscle proteomic and phosphoproteomic profile of Angus and Nellore. Seven animals of each breed previously subjected the same growth management were confined for 84 days. Proteins were extracted from Longissimus lumborum samples collected immediately after slaughter and separated by two-dimensional electrophoresis. Pro-Q Diamond stain was used in phosphoproteomics. Proteins identification was performed using matrix assisted laser desorption/ionization time-of-flight mass spectrometry. Tropomyosin alpha-1 chain, troponin-T, myosin light chain-1 fragment, cytoplasmic malate dehydrogenase, alpha-enolase and 78 kDa glucose-regulated protein were more abundant in Nellore, while myosin light chain 3, prohibitin, mitochondrial stress-70 protein and heat shock 70 kDa protein 6 were more abundant in Angus (P<0.05). Nellore had higher phosphorylation of myosin regulatory light chain-2, alpha actin-1, triosephosphate isomerase and 14-3-3 protein epsilon. However, Angus had greater phosphorylation of phosphoglucomutase-1 and troponin-T (P<0.05). Therefore, proteins involved in contraction and muscle organization, myofilaments expressed in fast or slow-twitch fibers and heat shock proteins localized in mitochondria or sarcoplasmic reticulum and involved in cell flux of calcium and apoptosis might be associated with differences in beef quality between Angus and Nellore. Furthermore, prohibitin appears to be a potential biomarker of intramuscular fat in cattle. Additionally, differences in phosphorylation of myofilaments and glycolytic enzymes could be involved with differences in muscle contraction force, susceptibility to calpain, apoptosis and postmortem glycolysis, which might also be related to differences in beef quality among Angus and Nellore.

Fig 1. Differentially abundant proteins in the Longissimus lumborum muscle of Angus and Nellore bulls.

Numbers found in the figure correspond to the Match ID shown in Table 1.

Fig 2. Differentially abundant phosphoproteins in the Longissimus lumborum muscle of Angus and Nellore bulls.

Numbers found in the figure correspond to the Match ID shown in Table 2.

Fig 3. Protein—protein interaction analysis of differentially abundant proteins and phosphoproteins between Angus and Nellore muscle.

Data have been elaborated and graphed through String 10.0. ATP-citrate synthase (ACLY), Mitochondrial malate dehydrogenase (MDH2), Cytoplasmic malate dehydrogenase (MDH1), Mitochondrial aspartate aminotransferase (GOT2), Phosphoglucomutase-1 (PGM1), Glucose-6-phosphate isomerase (GPI), Triosephosphate isomerase (TPI1), Pyruvate kinase (PKLR), Alpha-enolase (ENO1), M1-type pyruvate kinase (PKM), Phosphoglycerate kinase 1 (PGK1), Glyceraldehyde-3-phosphate dehydrogenase (G3PDH), Alpha skeletal muscle actin (ACTA1), Uncharacterized protein (CDC25B), M-phase inducer phosphatase 3 (CDC25C), 14-3-3 protein epsilon (YWHAE), Myosin regulatory light chain 2 (MYLPF), Myosin light chain 1/3 (MYL1), Cardiac troponin I (TNNI3), Uncharacterized protein (TNNI1), Fast troponin C type 2 (TNNC2), Tropomyosin alpha-1 chain (TPM1), Troponin T fast skeletal muscle type (TNNT3), Myosin light chain 3 (MYL3), TNNI2 protein (TNNI2), Cardiac troponin T (TNNT2), Mitochondrial GrpE protein homolog 1 (GRPEL1), Mitochondrial GrpE protein homolog 2 (GRPEL2), 78 kDa glucose-regulated protein (GRP78), Endoplasmin (HSP90B1), Mitochondrial stress-70 protein (HSPA9), Mitochondrial import inner membrane translocase subunit TIM44 (TIMM44), LOC615521 protein (LOC615521), Uncharacterized protein (HSPA6).