HIV-1 inhibitors from nature: understanding and optimizing potent cyanobacterial carbohydrate-binding proteins

Tuesday, October 25, 2011 — Poster Session II
Noon – 2:00 p.m.	Natcher Conference Center	NIDDK	MOLBIO-7

Authors

• S Loesgen
• S Shahzad-ul-Hussan
• CA Bewley

Abstract

Microorganisms are an excellent source of biologically active compounds, comprising over 50 % of all drug entities. Thus, the proteinaceous constituents from natural product represent a largely untapped source. Extremely stable and potent protein drug candidates disproved the widely held belief that bioactive proteins do not have the pharmacological characteristics necessary to become useful drugs. The HIV-inactivating cyanobacterial lectin cyanovirin-N (CVN) is a carbohydrate-binding protein that exhibits potent antiviral activity in nanomolar range with a remarkably degree of stability. Both, CVN and its homolog microvirin-N (MVN) exhibit high carbohydrate affinity for mannosides of the HIV-1 glycoprotein gp120 present on the viral envelope. Studies on CVN revealed two carbohydrate-binding sites of which only one is functional present in MVN. With a much better clinically safety profile for MVN, we hypothesize that installing the second carbohydrate-binding site in MVN through homology modeling and site-directed mutagenesis might increase antiviral potency. Further insight into the carbohydrate binding epitope of CVN is gained using NMR techniques to analyze the binding specificity of complex carbohydrates. Why cyanobacteria are producing these proteins is not well understood. Lab cultures of cyanobacteria analyzed with immuno-blot techniques are used to shed light on the natural occupation of our microbiocide candidates.

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