A mammalian homolog of SEC61p and SECYp is associated with ribosomes and nascent polypeptides during translocation

  title={A mammalian homolog of SEC61p and SECYp is associated with ribosomes and nascent polypeptides during translocation},
  author={Dirk G{\"o}rlich and Siegfried Prehn and Enno Hartmann and Kai-Uwe Kalies and Tom A. Rapoport},

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The Sec62–Sec63 translocon facilitates translocation of the C-terminus of membrane proteins

There is an unappreciated function of the Sec62–Sec63 translocon in regulating topogenesis of membrane proteins in the eukaryotic cell, according to systematic analysis of single and multi-spanning membrane proteins.

Evolutionary conservation of components of the protein translocation complex

The sequences of the β- and γ-subunits of the mammalian Sec61p complex are determined and seem to be key components of the protein translocation apparatus in all classes of organisms.

Mammalian Sec61 Is Associated with Sec62 and Sec63*

The existence of ribosome-free mammalian Sec61 complexes that associate with two ubiquitous proteins of the ER membrane that are named Sec62 and Sec63, respectively are reported here.

Alignment of conduits for the nascent polypeptide chain in the ribosome-Sec61 complex.

Cryo-electron microscopy of the ribosome-Sec61 complex and a three-dimensional reconstruction showed that the Sec61 oligomer is attached to the large ribosomal subunit by a single connection, strongly suggesting that both structures function together in the translocation of proteins across the endoplasmic reticulum membrane.

The bacterial SecY/E translocation complex forms channel-like structures similar to those of the eukaryotic Sec61p complex.

This work purifies a translocationally active complex of the two subunits, SecY and SecE, from Bacillus subtilis that forms ring structures in detergent solution and in intact lipid bilayers, often with a quasi-pentagonal appearance in projection.

A SecY Homolog in Arabidopsis thaliana

The nucleotide sequence of a full-length cDNA encoding a homolog of SecY from Arabidopsis thaliana is reported, and the predicted protein of 551 residues includes an amino-terminal extension of approximately 120 residues when compared with other SecY proteins.

Sec62p, a component of the endoplasmic reticulum protein translocation machinery, contains multiple binding sites for the Sec-complex.

SEC62 encodes an essential component of the Sec-complex that is responsible for posttranslational protein translocation across the membrane of the endoplasmic reticulum in Saccharomyces cerevisiae and it is shown that Sec62p binds via its cytosolic N- and C-terminal domains to theSec-complex.

Structure of the SecYEG Protein Translocation Complex

This chapter will review the recent structural results relating to the protein-conducting channel and the implications of these findings will be described in the context of the mechanism through which proteins pass across and into the membrane.



Assembly of yeast Sec proteins involved in translocation into the endoplasmic reticulum into a membrane-bound multisubunit complex

These results confirm previous predictions, based upon genetic interactions between the SEC genes, that Sec61, Sec62 and Sec63 act together to facilitate protein translocation into the ER.

Topology analysis of the SecY protein, an integral membrane protein involved in protein export in Escherichia coli.

The results suggest that SecY contains 10 transmembrane segments, five periplasmically exposed parts, and six cytoplasmic regions including the amino‐ and carboxyterminal regions.

SEC62 encodes a putative membrane protein required for protein translocation into the yeast endoplasmic reticulum

A potential membrane location for the SEC62 gene product is supported by evaluation of the molecular clone and DNA sequence analysis reveals a 32- kD protein with no obvious NH2-terminal signal sequence but with two domains of sufficient length and hydrophobicity to span a lipid bilayer.

Nucleotide sequence of the secY gene from Lactococcus lactis and identification of conserved regions by comparison of four SecY proteins

  • T. KoivulaIlkka PalvaHarri Hemilä
  • Biology, Medicine
    FEBS letters
  • 1991

The signal sequence of nascent preprolactin interacts with the 54K polypeptide of the signal recognition particle

This work shows for the first time a direct interaction between the signal sequence of a secretory protein and a component of SRP, the 54K polypeptide (relative molecular mass (Mr) 54,000), achieved by means of a new method of affinity labelling which involves the translational incorporation of an amino acid, carrying a photoreactive group, into nascentpolypeptides.

The secD locus of E.coli codes for two membrane proteins required for protein export.

The DNA sequence of the two genes along with alkaline phosphatase fusion analysis indicates that they code for integral proteins of the cytoplasmic membrane, suggesting that these two proteins may form a complex in the membrane which acts at late steps in the export process.

Identification of a ribosome receptor in the rough endoplasmic reticulum

Isolation of this domain has led to the identification, purification and characterization of the intact ribosome receptor, as well as its functional reconstitution into lipid vesicles.

A nascent membrane protein is located adjacent to ER membrane proteins throughout its integration and translation

Results show that the transmembrane segment of a nascent membrane protein is located adjacent to the mp39-like glycoprotein and other ER proteins during the integration process, and that at least a portion of the nascent chain remains in close proximity to these ER proteins until translation has been completed.