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Photoaffinity labeling of Ras converting enzyme using peptide substrates that incorporate benzoylphenylalanine (Bpa) residues: improved labeling and structural implications.

ABSTRACT: Rce1p catalyzes the proteolytic trimming of C-terminal tripeptides from isoprenylated proteins containing CAAX-box sequences. Because Rce1p processing is a necessary component in the Ras pathway of oncogenic signal transduction, Rce1p holds promise as a potential target for therapeutic intervention. However, its mechanism of proteolysis and active site have yet to be defined. Here, we describe synthetic peptide analogues that mimic the natural lipidated Rce1p substrate and incorporate photolabile groups for photoaffinity-labeling applications. These photoactive peptides are designed to crosslink to residues in or near the Rce1p active site. By incorporating the photoactive group via p-benzoyl-l-phenylalanine (Bpa) residues directly into the peptide substrate sequence, the labeling efficiency was substantially increased relative to a previously-synthesized compound. Incorporation of biotin on the N-terminus of the peptides permitted photolabeled Rce1p to be isolated via streptavidin affinity capture. Our findings further suggest that residues outside the CAAX-box sequence are in contact with Rce1p, which has implications for future inhibitor design.

SUBMITTER: Kyro K

PROVIDER: S-EPMC3319382 | biostudies-literature | 2011 Dec

REPOSITORIES: biostudies-literature

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Photoaffinity labeling of Ras converting enzyme using peptide substrates that incorporate benzoylphenylalanine (Bpa) residues: improved labeling and structural implications.

Kyro Kelly K Manandhar Surya P SP Mullen Daniel D Schmidt Walter K WK Distefano Mark D MD

Bioorganic & medicinal chemistry 20111018 24

Rce1p catalyzes the proteolytic trimming of C-terminal tripeptides from isoprenylated proteins containing CAAX-box sequences. Because Rce1p processing is a necessary component in the Ras pathway of oncogenic signal transduction, Rce1p holds promise as a potential target for therapeutic intervention. However, its mechanism of proteolysis and active site have yet to be defined. Here, we describe synthetic peptide analogues that mimic the natural lipidated Rce1p substrate and incorporate photolabil ...[more]

PMID: 22079863

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Project description:Angiotensin converting enzyme (ACE) is known for converting inactive angiotensin I into the potent vasoconstrictor angiotensin II, playing a critical role in blood pressure regulation. However, there is evidence that the dicarboxypeptidase activity of ACE is also essential for other physiological processes likely through processing of various peptide substrates. This study used mass spectrometry for the comprehensive detection and identification of natural substrates and products of ACE within the mouse plasma peptidome. The plasma peptidome of ACE KO mice was obtained through a multi-step purification process which included organic TCA precipitation as well as size exclusion and reversed phase chromatography. The obtained complex mixture of endogenous peptides was then subjected to in vitro cleavage by ACE. ACE-treated and untreated samples were then analyzed by LC/MS on an Orbitrap mass spectrometer, followed by alignment of MS1 data by Progenesis QI software. The MS1 signals that gained or lost intensity after treatment with ACE, were considered as possible products and substrates of ACE, respectively, and were selected for a targeted MS/MS analysis, and subsequently identified with PEAKS 8.5 and Proteome Discoverer software. Results. Close to 250 natural peptides were identified as possible substrates and products of ACE, demonstrating the high promiscuity of the enzyme. The use of internal standards as well as detection of some expected endogenous peptides, such as angiotensin II and bradykinin, supported the validity of the approach. Some of the newly identified substrates of ACE are known for their biological activities. For example, a fragment of complement C3, the 17-amino acid peptide C3f, exhibits spasminogenic activity and was processed by ACE. ACE cleavage of select peptides was further confirmed in vitro. Also, concentrations of ACE substrates in plasma from mice with variant genetic ACE domain backgrounds were determined by LC/MS using multiple reaction monitoring on a triple quadrupole mass spectrometer. The in vivo results were consistent with the in vitro results, in the sense that higher levels of the ACE substrates were observed when the respective processing domain was knocked out. The use of transgenic mice as well as ACE with single active domain allowed clarifying the ACE domain selectivity towards individual peptide substrates. This study resulted in creation of a library of substrates and products of ACE that can be further tested for their biological function and can help to elucidate the link between ACE and the numerous physiological effects attributed to its activity.

Dataset Information

Photoaffinity labeling of Ras converting enzyme using peptide substrates that incorporate benzoylphenylalanine (Bpa) residues: improved labeling and structural implications.

Publications

Photoaffinity labeling of Ras converting enzyme using peptide substrates that incorporate benzoylphenylalanine (Bpa) residues: improved labeling and structural implications.

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