<prompt> Defective proteins are degraded after attaching covalently to -ClathrinPepsinLamininUbiquitin  <response>: Ans. is d i.e., Ubiquitin o Defective proteins are often marked for destruction by ubiquitination attachment of small, highly conserved protein called ubiquitin. Such proteins are rapidly degraded by proteosome, which is a macromolecular, ATP dependent, proteolytic system located in the cytosol. 