Early encounters of a nascent membrane protein: specificity and timing of contacts inside and outside the ribosome.
An unbiased photo-cross-linking approach was used to probe the "molecular path" of a growing nascent Escherichia coli inner membrane protein (IMP) from the peptidyl transferase center to the surface of the ribosome. The nascent chain was initially in proximity to the ribosomal proteins L4 and L22 and subsequently contacted L23, which is indicative of progression through the ribosome via the main ribosomal tunnel. The signal recognition particle (SRP) started to interact with the nascent IMP and to target the ribosome-nascent chain complex to the Sec-YidC complex in the inner membrane when maximally half of the transmembrane domain (TM) was exposed from the ribosomal exit. The combined data suggest a flexible tunnel that may accommodate partially folded nascent proteins and parts of the SRP and SecY. Intraribosomal contacts of the nascent chain were not influenced by the presence of a functional TM in the ribosome.
Department of Molecular Microbiology, Institute of Molecular Cell Biology, Vrije Universiteit, 1081 HV Amsterdam, Netherlands.
Edith N G
EN
Houben
Raz
R
Zarivach
Bauke
B
Oudega
Joen
J
Luirink
D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism*; D029968:Escherichia coli Proteins / Q000096:biosynthesis* / Q000737:chemistry / Q000378:metabolism; D007425:Intracellular Membranes / Q000378:metabolism*; D046911:Macromolecular Substances / Q000378:metabolism; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism*; D026901:Membrane Transport Proteins / Q000378:metabolism; D008958:Models, Molecular; D017510:Protein Folding; D017434:Protein Structure, Tertiary / Q000502:physiology; D021122:Protein Subunits / Q000378:metabolism; D012269:Ribosomal Proteins / Q000378:metabolism; D012270:Ribosomes / Q000235:genetics / Q000378:metabolism*; D018271:Signal Recognition Particle / Q000235:genetics / Q000378:metabolism*; D013997:Time Factors
D029968:Escherichia coli Proteins; D046911:Macromolecular Substances; D008565:Membrane Proteins; D026901:Membrane Transport Proteins; D021122:Protein Subunits; D012269:Ribosomal Proteins; D018271:Signal Recognition Particle; C412443:YIDC protein, E coli; C056368:ribosomal protein L4