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

Date Published: January 19, 2017

Publisher: Public Library of Science

Author(s): Rafael Torres de Souza Rodrigues, Mario Luiz Chizzotti, Camilo Elber Vital, Maria Cristina Baracat-Pereira, Edvaldo Barros, Karina Costa Busato, Rafael Aparecido Gomes, Márcio Machado Ladeira, Taiane da Silva Martins, Juan J Loor.

http://doi.org/10.1371/journal.pone.0170294

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.

Partial Text

Brazil is the second largest producer and one of the largest beef exporters in the world [1]. The majority of the Brazilian herd is composed of Zebu cattle (Bos taurus indicus), mainly the Nellore breed. Zebu beef is usually less tender and has less marbling than that of taurine cattle (Bos taurus taurus), particularly the Angus breed [2, 3]. This reduces attractiveness of zebu beef, because tenderness and marbling are considered the main palatability characteristics by consumers [4].

A total of 423 matches ID were detected in the analysis of total protein and 1,093 in the analysis of phosphorylated proteins, of which 38 and 55 differed (P<0.05) between breeds, respectively. Excision of differentially abundant spots was only performed for clearly visible and separable spots on gels (36 in the proteomic analysis and 23 in the phosphoproteomic study). Due to the 2DE/MS limitations for identification of low abundance proteins, it was not possible to identify all spots that were excised. We can conclude that differences in proteins involved with 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 content in cattle. In addition, differences in phosphorylation of myofilaments and glycolytic enzymes could be involved in 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.   Source: http://doi.org/10.1371/journal.pone.0170294

 

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