Does the channel for nascent peptide exist inside the ribosome? Immune electron microscopy study.
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.
Ryabova
L A
LA
Institute of Protein Research, Academy of Sciences of the USSR, Pushchino, Moscow Region.
Selivanova
O M
OM
Baranov
V I
VI
Vasiliev
V D
VD
Spirin
A S
AS
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
D000906:Antibodies; D000936:Antigen-Antibody Complex