TY - JOUR
T1 - Mechanism of farnesylated CAAX protein processing by the intramembrane protease Rce1
AU - Manolaridis, Ioannis
AU - Kulkarni, Kiran
AU - Dodd, Roger B.
AU - Ogasawara, Satoshi
AU - Zhang, Ziguo
AU - Bineva, Ganka
AU - O'Reilly, Nicola
AU - Hanrahan, Sarah J.
AU - Thompson, Andrew J.
AU - Cronin, Nora
AU - Iwata, So
AU - Barford, David
N1 - Funding Information:
Acknowledgements This work was funded by a Cancer Research UK grant to D.B. Part of this work was supported by the research acceleration program of the Japan Science and Technology agency and by BBSRC BB/G023425/1 (S.I.). We thank staff at the I04-1 Diamond Light Source for help with data collection, J. Yang for advice and discussions, I. De Moraes for support and T. Daviter for help with the circular dichroism experiments.
PY - 2013
Y1 - 2013
N2 - CAAX proteins have essential roles in multiple signalling pathways, controlling processes such as proliferation, differentiation and carcinogenesis. The ∼120 mammalian CAAX proteins function at cellular membranes and include the Ras superfamily of small GTPases, nuclear lamins, the γ-subunit of heterotrimeric GTPases, and several protein kinases and phosphatases. The proper localization of CAAX proteins to cell membranes is orchestrated by a series of post-translational modifications of the carboxy-terminal CAAX motifs (where C is cysteine, A is an aliphatic amino acid and X is any amino acid). These reactions involve prenylation of the cysteine residue, cleavage at the AAX tripeptide and methylation of the carboxyl-prenylated cysteine residue. The major CAAX protease activity is mediated by Rce1 (Ras and a-factor converting enzyme 1), an intramembrane protease (IMP) of the endoplasmic reticulum. Information on the architecture and proteolytic mechanism of Rce1 has been lacking. Here we report the crystal structure of a Methanococcus maripaludis homologue of Rce1, whose endopeptidase specificity for farnesylated peptides mimics that of eukaryotic Rce1. Its structure, comprising eight transmembrane α-helices, and catalytic site are distinct from those of other IMPs. The catalytic residues are located ∼10 Å into the membrane and are exposed to the cytoplasm and membrane through a conical cavity that accommodates the prenylated CAAX substrate. We propose that the farnesyl lipid binds to a site at the opening of two transmembrane α-helices, which results in the scissile bond being positioned adjacent to a glutamate-activated nucleophilic water molecule. This study suggests that Rce1 is the founding member of a novel IMP family, the glutamate IMPs.
AB - CAAX proteins have essential roles in multiple signalling pathways, controlling processes such as proliferation, differentiation and carcinogenesis. The ∼120 mammalian CAAX proteins function at cellular membranes and include the Ras superfamily of small GTPases, nuclear lamins, the γ-subunit of heterotrimeric GTPases, and several protein kinases and phosphatases. The proper localization of CAAX proteins to cell membranes is orchestrated by a series of post-translational modifications of the carboxy-terminal CAAX motifs (where C is cysteine, A is an aliphatic amino acid and X is any amino acid). These reactions involve prenylation of the cysteine residue, cleavage at the AAX tripeptide and methylation of the carboxyl-prenylated cysteine residue. The major CAAX protease activity is mediated by Rce1 (Ras and a-factor converting enzyme 1), an intramembrane protease (IMP) of the endoplasmic reticulum. Information on the architecture and proteolytic mechanism of Rce1 has been lacking. Here we report the crystal structure of a Methanococcus maripaludis homologue of Rce1, whose endopeptidase specificity for farnesylated peptides mimics that of eukaryotic Rce1. Its structure, comprising eight transmembrane α-helices, and catalytic site are distinct from those of other IMPs. The catalytic residues are located ∼10 Å into the membrane and are exposed to the cytoplasm and membrane through a conical cavity that accommodates the prenylated CAAX substrate. We propose that the farnesyl lipid binds to a site at the opening of two transmembrane α-helices, which results in the scissile bond being positioned adjacent to a glutamate-activated nucleophilic water molecule. This study suggests that Rce1 is the founding member of a novel IMP family, the glutamate IMPs.
UR - http://www.scopus.com/inward/record.url?scp=84890441584&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=84890441584&partnerID=8YFLogxK
U2 - 10.1038/nature12754
DO - 10.1038/nature12754
M3 - Article
C2 - 24291792
AN - SCOPUS:84890441584
VL - 504
SP - 301
EP - 305
JO - Nature
JF - Nature
SN - 0028-0836
IS - 7479
ER -