2GED

Signal Recognition Particle Receptor Beta-Subunit in nucleotide-free dimerized form

Summary for 2GED

• Entry DOI: 10.2210/pdb2ged/pdb
• Descriptor: Signal recognition particle receptor beta subunit, SULFATE ION (3 entities in total)
• Functional Keywords: protein transport, g protein, signal recognition particle, proline isomerization, circular permutation, signaling protein
• Biological source: Saccharomyces cerevisiae (baker's yeast); More
• Cellular location: Endoplasmic reticulum membrane : P36057
• Total number of polymer chains: 2
• Total formula weight: 42798.62

Authors

Schmidt, D.,Schwartz, T.U. (deposition date: 2006-03-19, release date: 2006-04-18, Last modification date: 2023-08-30)

Primary citation

Schwartz, T.U.,Schmidt, D.,Brohawn, S.G.,Blobel, G.
Homodimerization of the G protein SR{beta} in the nucleotide-free state involves proline cis/trans isomerization in the switch II region.
Proc.Natl.Acad.Sci.USA, 103:6823-6828, 2006

PubMed Abstract: Protein translocation across and insertion into membranes is essential to all life forms. Signal peptide-bearing nascent polypeptide chains emerging from the ribosome are first sampled by the signal-recognition particle (SRP), then targeted to the membrane via the SRP receptor (SR), and, finally, transferred to the protein-conducting channel. In eukaryotes, this process is tightly controlled by the concerted action of three G proteins, the 54-kD subunit of SRP and the alpha- and beta-subunits of SR. We have determined the 2.2-A crystal structure of the nucleotide-free SRbeta domain. Unexpectedly, the structure is a homodimer with a highly intertwined interface made up of residues from the switch regions of the G domain. The remodeling of the switch regions does not resemble any of the known G protein switch mechanisms. Biochemical analysis confirms homodimerization in vitro, which is incompatible with SRalpha binding. The switch mechanism involves cis/trans isomerization of a strictly conserved proline, potentially implying a new layer of regulation of cotranslational transport.

PubMed: 16627619
DOI: 10.1073/pnas.0602083103

Experimental method

X-RAY DIFFRACTION (2.2 Å)