Title

Interaction of CTX-M-15 enzyme with cefotaxime: a molecular modelling and docking study

Authors

Shazi Shakil, Asad Ullah Khan^*

Affiliation

Interdisciplinary Biotechnology Unit, Aligarh Muslim University, Aligarh-202002, Interdisciplinary Biotechnology Unit, Aligarh Muslim University Aligarh 202002, India

Email

asad.k@rediffmail.com

Article Type

Hypothesis

Date

Received ; revised ; accepted ; published April 30, 2010

Abstract

Extended-spectrum β-lactamases (ESBLs) are the bacterial enzymes that make them resistant to advanced-generation cephalosporins. CTXM enzymes (the most prevalent ESBL-type) target cefotaxime. Aims of the study were: (i) Modelling of CTX-M enzyme from bla_CTX-M sequences of clinical Escherichia coli isolates (ii) Docking of cefotaxime with modelled CTX-M enzymes to identify amino acid residues crucial to their interaction (iii) To hypothesize a possible relationship between ‘interaction energy of the docked enzyme-antibiotic complex’ and ‘minimum inhibitory concentration (MIC) of the antibiotic against the bacteria producing that enzyme’. Seven E. coli strains of clinical origin which were confirmed as PCR-positive for blaCTX-M were selected for the study. C600 cells harboring cloned bla_CTX-M were tested for ESBL-production by double-disk-synergy test. BLAST analysis confirmed all the bla_CTX-M genes as bla_CTX-M-15. Four of the 7 strains were found to be clonally related. Modelling was performed using Swiss Model Server. Discovery Studio 2.0 (Accelrys) was used to prepare Ramachandran plots for the modelled structures. Ramachandran Z-scores for modelled CTX-M enzymes from E. coli strains D8, D183, D253, D281, D282, D295 and D296 were found to be -0.449, 0.096, 0.027, 0.043, 0.032, -1.249 and -1.107, respectively. Docking was performed using Hex 5.1 and the results were further confirmed by Autodock 4.0. The amino acid residues Asn 104, Asn132, Gly 227, Thr 235, Gly 236, and Ser237 were found to be responsible for positioning cefotaxime into the active site of the CTX-M-15 enzyme. It was found that cefotaxime MICs for the CTX-M-15-producers increased with the increasing negative interaction energy of the enzyme-antibiotic complex.
 

Keywords

antibiotic resistance; CTX-M; docking; extended-spectrum β-lactamases; modelling.

Citation

Shakil & Khan, Bioinformation 4(10): 000-000 (2010)

Edited by

N. Srinivasan

ISSN

0973-2063

Publisher

Biomedical Informatics

License

This is an Open Access article which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly credited. This is distributed under the terms of the Creative Commons Attribution License.