Function of ubiquitin in the cell is:

Ref: Koeppen BM, Stanton BA. Skeletal Muscle Physiology. In: Berne & Levy Physiology 6th ed. Mosby; 2008 p 250. & Hershko A, Ciechanover A. The uhiquitin system. Anna Rev Biochem. 1998:67:425-79.Explanation:"One factor thought to contribute to the decreased protein synthesis and increased protein degradation during periods of mechanical inactivity is the release of a ubiquitin ligase (MuRF2) from titin. MuRF2 also promotes protein degradation through ubiquitination "The ubiquitin systemThe selective degradation of many short-lived proteins in eukaryotic cells is carried out by the ubiquitin system.In this pathway, proteins are targeted for degradation by covalent ligation to ubiquitin. a highly conserved small protein.UBIQUITIN-mediated degradation of regulatory- proteins plays important roles in:Cell-cycle progressionSignal transductionTranscriptional regulationReceptor dow n-regulationEndocytosisImmune responseDevelopmentProgrammed cell death (Apoptosis)