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Isolation, characterization, and recombinant production of a novel anti-HIV protein, Cnidarin1

Tuesday, October 25, 2011 — Poster Session II

Noon – 2:00 p.m.

Natcher Conference Center




  • K Ramessar
  • L Krumpe
  • CY Xiong
  • J Wilson
  • JB McMahon
  • BR O’Keefe


We isolated a novel protein Cnidarin1 (CNID1) from an aqueous extract of the soft coral Synthecium sp. that shows potent nanomolar anti-HIV activity. The sequenced 172 amino acid protein is a monomer of 18,122-Da and has a high β-sheet content. For recombinant production, a synthetic gene (optimized for E.coli codon preference) was cloned into a suitable vector system for cytosolic expression of CNID1 (tagged N-terminally with hexa-histidine) in E.coli. Expression induced with IPTG at 37˚C yielded low cytosolic amounts of His-rCNID1 which when purified (metal affinity resin column), showed no anti-HIV activity. Circular dichroism analysis show that His-rCNID1 has less β-sheet and more random coil structure than native CNID1, indicating incorrect folding. Attempts to refold insoluble His-rCNID1 (from inclusion bodies) resulted in partial anti-HIV activity. The use of lower temperature (25˚C) for expression did not increase the quantity of soluble His-rCNID1, but when purified, His-rCNID1 was smaller (14.5kDa) and showed potent anti-HIV activity comparable to native CNID1. Secondary structure analysis estimate similar structures for the cleaved 14.5kDa His-rCNID1 when compared to native CNID1. Future work will focus on isolating large quantities of rCNID1 for further structural and preclinical studies.

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