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Structural basis for the C-domain selective angiotensin converting enzyme inhibition by bradykinin-potentiating peptide b (BPPb)

DOI: 10.1042/BCJ20190290 DOI Help

Authors: Edward D. Sturrock (University of Cape Town) , Lizelle Lubbe (University of Cape Town) , Gyles E. Cozier (University of Bath) , Sylva L. U. Schwager (University of Bath) , Afolake T. Arowolo (University of Cape Town) , Lauren B. Arendse (University of Cape Town) , Emma Ruth Belcher (University of Bristol) , K. Ravi Acharya (University of Bath)
Co-authored by industrial partner: No

Type: Journal Paper
Journal: Biochemical Journal

State: Published (Approved)
Published: May 2019
Diamond Proposal Number(s): 17212

Open Access Open Access

Abstract: Angiotensin-converting enzyme (ACE) is a zinc metalloprotease best known for its role in blood pressure regulation. ACE consists of two homologous catalytic domains, the N- and C-domain, that display distinct but overlapping catalytic functions in vivo owing to subtle differences in substrate specificity. While current generation ACE inhibitors target both ACE domains, domain-selective ACE inhibitors may be clinically advantageous, either reducing side-effects or having utility in new indications. Here, we used site-directed mutagenesis, an ACE chimera and X-ray crystallography to unveil the molecular basis for C-domain selective ACE inhibition by the bradykinin potentiating peptide b (BPPb), naturally present in Brazilian pit viper venom. We present the BPPb-N-domain structure in comparison with the previously reported BPPb-C-domain structure and highlight key differences in peptide interactions with the S4 to S9 subsites. This suggests involvement of these subsites in conferring C-domain selective BPPb binding, in agreement with the mutagenesis results where unique residues governing differences in active site exposure, lid structure and dynamics between the two domains were the major drivers for C-domain selective BPPb binding. Mere disruption of BPPb interactions with unique S2 and S4 subsite residues, which synergistically assist in BPPb binding, was insufficient to abolish C-domain selectivity. The combination of unique S9-S4 and S2สน subsite C-domain residues were required for the favourable entry, orientation and thus, selective binding of the peptide. This emphasizes the need to consider factors other than direct protein-inhibitor interactions to guide the design of domain-selective ACE inhibitors, especially in the case of larger peptides.

Journal Keywords: Zinc metalloprotease; Site-directed mutagenesis; heterologous mammalian protein expression; X-ray crystallography; fluorogenic assays

Subject Areas: Biology and Bio-materials, Chemistry

Instruments: I04-Macromolecular Crystallography


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