title: Does the channel for nascent peptide exist inside the ribosome? Immune electron microscopy study.
abstract: MS2 phage RNA-directed synthesis of an N-terminal polypeptide of the phage coat protein on Escherichia coli 70 S ribosomes was initiated in a cell-free system with the N-dinitrophenyl derivative of methionyl-tRNAFMet) and performed in the absence of tyrosine, lysine, cysteine and methionine. As a result, the translating ribosomes carried peptides up to 42 amino acid residues in length with the dinitrophenyl hapten at the N-ends. Using the immune electron microscopy technique the positions of the nascent peptide N-ends on the 70 S ribosomes have been visualized. It has been found that (i) the N-ends of nascent peptides of these lengths are accessible to antibodies, (ii) the exit site of a nascent peptide is the pocket between the base of the central protuberance and the L1 ridge on the 50 S subunit, i.e. presumably its peptidyl transferase center, and (iii) the further pathway of a nascent peptide seems to proceed along the groove on the external surface of the 50 S subunit.
authors.affiliation: Institute of Protein Research, Academy of Sciences of the USSR, Pushchino, Moscow Region.
authors.forename: L A
authors.initials: LA
authors.lastname: Ryabova
authors.forename: O M
authors.initials: OM
authors.lastname: Selivanova
authors.forename: V I
authors.initials: VI
authors.lastname: Baranov
authors.forename: V D
authors.initials: VD
authors.lastname: Vasiliev
authors.forename: A S
authors.initials: AS
authors.lastname: Spirin
mesh_terms: D000906:Antibodies; D000936:Antigen-Antibody Complex / Q000032:analysis; D002474:Cell-Free System; D003090:Coliphages / Q000235:genetics / Q000378:metabolism; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism* / Q000648:ultrastructure; D008854:Microscopy, Electron; D010452:Peptide Biosynthesis; D014176:Protein Biosynthesis; D012270:Ribosomes / Q000378:metabolism* / Q000648:ultrastructure
chemical_list: D000906:Antibodies; D000936:Antigen-Antibody Complex