Protein Synthesis and Secretion as Seen by the Nascent Protein Chain

摘要: One of the features that distinguishes ribosome from most other enzymes is need to retain product each transpeptidation reaction, specifically nascent or growing polypeptide chain, until mRNA-dependent polymerization amino acids terminated by a stop codon. Since many proteins are more than 1000 in length, space occupied chain attached ribosome-bound peptidyl-tRNA can be substantial. The must therefore designed minimize interference between and molecular traffic associated with decoding protein elongation (tRNA factors). probable solution this structural issue was provided Malkin Rich (1967) Blobel Sabatini (1970), who found protected C-terminal 40 so proteolytic digestion. This suggested not exposed cytoplasm near peptidyltransferase center, but instead left far its active site. model later supported immunoelectron microscopy data detected folding outside at base large ribosomal subunit (Bernabeu Lake, 1982) x-ray diffraction revealed region low electron density extended approximately center located central protuberance (Yonath et al., 1987).