Design and exploration of novel boronic acid Inhibitors reveals important Interactions with a clavulanic acid-resistant sulfhydryl- variable (SHV) β‑ lactamase

Inhibitor resistant (IR) class A β -lactamases pose a signi fi cant threat to
many current antibiotic combinations. The K234R substitution in the SHV β -lactamase,
from Klebsiella pneumoniae, results in resistance to ampicillin/clavulanate. After site-
saturation mutagenesis of Lys-234 in SHV, microbiological and biochemical character-
ization of the resulting β -lactamases revealed that only − Arg conferred resistance to
ampicillin/clavulanate. X-ray crystallography revealed two conformations of Arg-234 and
Ser-130 in SHV K234R. The movement of Ser-130 is the principal cause of the observed
clavulanate resistance. A panel of boronic acid inhibitors was designed and tested against
SHV-1 and SHV K234R. A chiral ampicillin analogue was discovered to have a 2.4 ± 0.2
nM K i for SHV K234R; the chiral ampicillin analogue formed a more complex hydrogen-
bonding network in SHV K234R vs SHV-1. Consideration of the spatial position of Ser-
130 and Lys-234 and this hydrogen-bonding network will be important in the design of
novel antibiotics targeting IR β -lactamases.