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Behavior of nascent polypeptide chains in and on the ribosome
Author(s) -
Beckmann Roland
Publication year - 2009
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.23.1_supplement.203.2
Subject(s) - ribosome , protein subunit , biophysics , chain (unit) , chemistry , crystallography , physics , biology , rna , biochemistry , astronomy , gene
The earliest environment a nascent polypeptide chain will encounter is the ribosomal tunnel through the large ribosomal subunit. In all kingdoms of life this tunnel has the same dimensions with a length of ca 100 Angstroms and a width ranging from 10 to 20 Angtsroms. After the first third of the tunnel a constriction is present and the last third adopts a funnel like widening towards the exit. In most cases the nascent polypeptide is thought to move through the tunnel without engaging in specific interactions with the tunnel wall. However, certain nascent chains can interact with the tunnel wall in order to stall the translational machinery. Other nascent chains may adopt secondary structure already inside the tunnel in order to specifically initiate folding before emerging from the tunnel. Moreover, it has been proposed that specific nascent chains such as hydrophobic transmembrane domains can trigger allosteric regulation of ribosomal ligands bound at the tunnel exit. Here, we present cryo‐electron microscopic (cryo‐EM) structures of several ribosome‐nascent chain complexes at sub‐nanometer resolution. We observe distinct conformations and interaction patterns for stalling nascent chains and, in addition, secondary structure formation in the tunnel.