Download Biochemical Analysis of the Binding Interaction between LanI and its

Biochemical Analysis of the Binding Interaction between LanI and its
Cognate Lantibiotic in Bacillus subtilis and Lactococcus lactis
Isabel Neacato, MD/PhD candidate, Microbiology, University of Illinois at
Urbana-Champaign, Urbana, Ian Gut, PhD, Microbiology, University of
Illinois at Urbana-Champaign, Urbana, IL and Wilfred van der Donk, PhD,
Chemistry, University of Illinois at Urbana-Champaign, Urbana, IL
Abstract:
Lantibiotics are a group of ribosomally synthesized antimicrobial peptides
produced by Gram-positive bacteria. The lantibiotics subtilin and nisin both
target lipid II inhibiting bacterial cell wall biogenesis. To protect the cell
against their actively secreted product, the lantibiotic producing strains,
Bacillus subtilis (subtilin) and Lactococcus lactis (nisin) produce selfresistance proteins, generally annotated, LanI and LanFEG, that confer
protection against the lantibiotics they produce. LanI, a peripheral
membrane protein located on the extracellular cytoplasmic side has been
shown to bind its cognate lantibiotic to prevent its binding to lipid II.
Previous studies have shown that despite the similar amino acid sequence
and ring topology conformation between nisin and subtilin, NisI (L. lactis)
is only able to interact with nisin (KD of 0.6 - 2.0 uM), but not subtilin,
indicating the specificity of LanI proteins. SpaI (B. subtilis), which shares
17% sequence homology to NisI, has also been shown to specifically
interact with subtilin, however the KD has not been determined. In order to
study the LanI-lantibiotic interaction in vitro, nisin, subtilin and their selfresistance proteins have been purified. Studies on the thermodynamics
and structural changes of LanI, in the absence and presence of its cognate
lantibiotic will be studied by isothermal titration calorimetry and circular
dichroism analysis, respectively. These studies will shed light on important
binding interactions between LanI proteins and their cognate lantibiotic
and the mechanisms by which they help to confer protection to the
bacterial cell.