Biophysical Society Thematic Meeting - November 16-20, 2015

Biophysics in the Understanding, Diagnosis, and Treatment of Infectious Diseases Poster Abstracts

8-POS Board 8 Structural and Functional Effects of Nucleotide Variation on the Tuberculosis Drug Metabolizing Enzyme Human Arylamine N-Acetyltransferase 1 Protein Ruben Cloete 1 , Wisdom Akurugu 1,3 , Cedric Werely 2 , Alan Christoffels 1 . 1 University of the western cape, Cape Town, Western Cape, South Africa, 2 University of Stellenbosch, Cape Town, South Africa, 3 University of Ghana, Accra, Ghana. The human arylamine N-acetyltransferase 1 (NAT1) determine the duration of action of amine- containing drugs by influencing the balance between detoxification and metabolic activation of these drugs. Single nucleotide polymorphisms (SNPs) in NAT1 have been implicated in inter- ethnic and inter-individual variation of phenotypic profiles in patients being treated for tuberculosis (TB). The effects of six non-synonymous SNPs on the structure and function of NAT1 was tested. Atomistic simulation studies and stability calculations using both GROMACS and Site Directed mutator (SDM) were performed to supplement the routinely used SIFT and POLYPHEN-2 algorithms. Analysis of the four novel SNPs identified within South African mixed ancestry population revealed two (N245I and V231G) that affect NAT1 protein function while the other two (R242M and E264K) showed contradictory results. To determine the effect of mutations on stability of the protein structure, we used the crystal structure of NAT1 (PDBID: 2IJA) as the wild type structure and modified the cysteine 68 residue to be acetylated in complex with coenzyme A and para-aminobenzoic acid. The wild type and mutant structures were submitted to the web-server SDM. Three of the novel SNPs showed slightly to highly destabilizing effects (-0.58 to -5.09kcal/mol) while the experimentally validated SNPs associated with fast and slow acetylation (I263V and R64W) showed destabilizing and stabilizing effects -0.98 and 1.19kcal/mol, respectively. For a conclusive result, we propose the use of simulation studies to quantify the effect of SNPs on the protein structures and function using appropriate measures. This may be validated with in- vitro experiments. Findings from this study might inform a strategy of incorporating genotypic data (i.e, functional SNP alleles) with phenotypic information (slow or fast acetylators) to better prescribe effective tuberculosis treatment.

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