Analysis of mutations leading to para-aminosalicylic acid resistance in Mycobacterium tuberculosis

Bharati Pandey,Abhinav Grover,Jagdeep Kaur,Sonam Grover

doi:10.1038/s41598-019-48940-5

Abstract

Thymidylate synthase A (ThyA) is the key enzyme involved in the folate pathway in Mycobacterium tuberculosis. Mutation of key residues of ThyA enzyme which are involved in interaction with substrate 2′-deoxyuridine-5′-monophosphate (dUMP), cofactor 5,10-methylenetetrahydrofolate (MTHF), and catalytic site have caused para-aminosalicylic acid (PAS) resistance in TB patients. Focusing on R127L, L143P, C146R, L172P, A182P, and V261G mutations, including wild-type, we performed long molecular dynamics (MD) simulations in explicit solvent to investigate the molecular principles underlying PAS resistance due to missense mutations. We found that these mutations lead to (i) extensive changes in the dUMP and MTHF binding sites, (ii) weak interaction of ThyA enzyme with dUMP and MTHF by inducing conformational changes in the structure, (iii) loss of the hydrogen bond and other atomic interactions and (iv) enhanced movement of protein atoms indicated by principal component analysis (PCA). In this study, MD simulations framework has provided considerable insight into mutation induced conformational changes in the ThyA enzyme of Mycobacterium.

Highlights

Antimicrobial resistance (AMR) threatens the effective treatment of tuberculosis (TB) caused by the bacteria Mycobacterium tuberculosis (Mtb) and has become a serious threat to global public health[1]
Thymidylate synthase A (ThyA) enzyme catalyzes the conversion of 2′-deoxyuridine-5′-monophosphate to 2′ deoxythymidine-5′-monophosphate as follows: 5, 10 − methylenetetrahydrofolate + dUMP = dTMP + dihydrofolate
The folate pathway is reported to be very important for the growth and survival of the bacteria

Summary

Introduction

Antimicrobial resistance (AMR) threatens the effective treatment of tuberculosis (TB) caused by the bacteria Mycobacterium tuberculosis (Mtb) and has become a serious threat to global public health[1]. PAS resistance was reported in strains of M. tuberculosis due to various missense mutations in the 7,8-dihydrofolate monoglutamate (H2Pte-Glu) binding pocket of the dihydrofolate synthase (DHFS) (encoded by the folC gene). Rengarajan et al.[13] first reported that Mycobacterium develops PAS resistance due to mutations present in the thymidylate synthase A gene (thyA) using transposon mutagenesis[13]. Twenty novel PAS resistance mutations in thyA gene have been reported in the Mtb clinical isolates from Northern China[15]. Mtb has two different types of thymidylate synthase (TS) enzymes, ThyA and ThyX. The Mtb genome with a deleted thyA gene conferred PAS resistance and showed defective in vitro growth but normal in vivo growth[16]. ThyA (EC 2.1.1.45) enzyme (encoded by the thyA gene) plays a significant role in thymine biosynthesis in folate pathway.

Methods

Results

Conclusion