NAC covers ribosome-associated nascent chains thereby forming a protective environment for regions of nascent chains just emerging from the peptidyl transferase center.
We demonstrate that nascent polypeptide-associated complex (NAC) is one of the first cytosolic factors that newly synthesized nascent chains encounter. When NAC is present, nascent chains are segregated from the cytosol until approximately 30 amino acids in length, a finding consistent with the well-documented protease resistance of short ribosome-associated nascent chains. When NAC is removed, the normally protected nascent chains are susceptible to proteolysis. Therefore NAC, by covering COOH-terminal segments of nascent chains on the ribosome, perhaps together with ribosomal proteins, forms a protective environment for regions of nascent chains just emerging from the peptidyl transferase center. Since NAC is not a core ribosomal protein, the emergence of nascent chains from the ribosome may be more dynamic than previously thought.
Wang
S
S
Cellular Biochemistry and Biophysics Program, Memorial Sloan-Kettering Cancer Center, New York 10021, USA.
Sakai
H
H
Wiedmann
M
M
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D002474:Cell-Free System; D003432:Cross-Linking Reagents; D015951:Factor Xa / Q000494:pharmacology; D008969:Molecular Sequence Data; D010441:Peptide Chain Elongation, Translational / Q000502:physiology*; D010442:Peptide Chain Initiation, Translational / Q000502:physiology*; D010446:Peptide Fragments / Q000187:drug effects / Q000378:metabolism; D010458:Peptidyl Transferases / Q000378:metabolism*; D011485:Protein Binding; D011506:Proteins / Q000378:metabolism; D011817:Rabbits; D012156:Reticulocytes / Q000378:metabolism; D012269:Ribosomal Proteins / Q000378:metabolism; D012270:Ribosomes / Q000378:metabolism* / Q000648:ultrastructure; D012639:Seeds / Q000378:metabolism
D003432:Cross-Linking Reagents; D010446:Peptide Fragments; D011506:Proteins; D012269:Ribosomal Proteins; D010458:Peptidyl Transferases; D015951:Factor Xa