Membrane topology of S2P, a protein required for intramembranous cleavage of sterol regulatory element-binding proteins

Nikolai G. Zelenski, Robert B. Rawson, Michael S. Brown, Joseph L. Goldstein

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87 Citations (Scopus)

Abstract

In sterol-depleted mammalian cells, a two-step proteolytic process releases the NH2-terminal domains of sterol regulatory element-binding proteins (SREBPs) from membranes of the endoplasmic reticulum (ER). These domains translocate into the nucleus, where they activate genes of cholesterol and fatty acid biosynthesis. The SREBPs are oriented in the membrane in a hairpin fashion, with the-NH2-and COOH-terminal domains facing the cytosol and a single hydrophilic loop projecting into the lumen. The first cleavage occurs at Site-1 within the ER lumen to generate an intermediate that is subsequently released from the membrane by cleavage at Site-2, which lies within the first transmembrane domain. A membrane protein, designated S2P, a putative zinc metalloprotease, is required for this cleavage. Here, we use protease protection and glycosylation site mapping to define the topology of S2P in ER membranes. Both the NH2 and COOH termini of S2P face the cytosol. Most of S2P is hydrophobic and appears to be buried in the membrane. All three of the long hydrophilic sequences of S2P can be glycosylated, indicating that they all project into the lumen. The HEIGH sequence of S2P, which contains two potential zinc-coordinating residues, is contained within a long hydrophobic segment. Aspartic acid 467, located ~300 residues away from the HEIGH sequence, appears to provide the third coordinating residue for the active site zinc. This residue, too, is located in a hydrophobic sequence. The hydrophobicity of these sequences suggests that the active site of S2P is located within the membrane in an ideal position to cleave its target, a Leu-Cys bond in the first transmembrane helix of SREBPs.

Original languageEnglish (US)
Pages (from-to)21973-21980
Number of pages8
JournalJournal of Biological Chemistry
Volume274
Issue number31
DOIs
StatePublished - Jul 30 1999

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Sterol Regulatory Element Binding Proteins
Topology
Membranes
Endoplasmic Reticulum
Zinc
Proteins
Cytosol
Catalytic Domain
Glycosylation
Biosynthesis
Metalloproteases
Sterols
Hydrophobicity
Hydrophobic and Hydrophilic Interactions
Aspartic Acid
Membrane Proteins
Peptide Hydrolases
Fatty Acids
Genes
Cholesterol

ASJC Scopus subject areas

  • Biochemistry

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Membrane topology of S2P, a protein required for intramembranous cleavage of sterol regulatory element-binding proteins. / Zelenski, Nikolai G.; Rawson, Robert B.; Brown, Michael S.; Goldstein, Joseph L.

In: Journal of Biological Chemistry, Vol. 274, No. 31, 30.07.1999, p. 21973-21980.

Research output: Contribution to journalArticle

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