title: Atomic Insight into the Altered O6-Methylguanine-DNA Methyltransferase Protein Architecture in Gastric Cancer.
abstract: O6-methylguanine-DNA methyltransferase (MGMT) is one of the major DNA repair protein that counteracts the alkalyting agent-induced DNA damage by replacing O6-methylguanine (mutagenic lesion) back to guanine, eventually suppressing the mismatch errors and double strand crosslinks. Exonic alterations in the form of nucleotide polymorphism may result in altered protein structure that in turn can lead to the loss of function. In the present study, we focused on the population feared for high exposure to alkylating agents owing to their typical and specialized dietary habits. To this end, gastric cancer patients pooled out from the population were selected for the mutational screening of a specific error prone region of MGMT gene. We found that nearly 40% of the studied neoplastic samples harbored missense mutation at codon151 resulting into Serine to Isoleucine variation. This variation resulted in bringing about the structural disorder, subsequently ensuing into a major stoichiometric variance in recognition domain, substrate binding and selectivity loop of the active site of the MGMT protein, as observed under virtual microscope of molecular dynamics simulation (MDS). The atomic insight into MGMT protein by computational approach showed a significant change in the intra molecular hydrogen bond pattern, thus leading to the observed structural anomalies. To further examine the mutational implications on regulatory plugs of MGMT that holds the protein in a DNA-Binding position, a MDS based analysis was carried out on, all known physically interacting amino acids essentially clustered into groups based on their position and function. The results generated by physical-functional clustering of protein indicated that the identified mutation in the vicinity of the active site of MGMT protein causes the local and global destabilization of a protein by either eliminating the stabilizing salt bridges in cluster C3, C4, and C5 or by locally destabilizing the "protein stabilizing hing" mapped on C3-C4 cluster, preceding the active site.
authors.affiliation: Division of Medical Biotechnology, School of Bioscience and Technology, VIT University, Vellore, Tamil Nadu, 632014, India; Departments of Biotechnology, University of Kashmir, Srinagar, Kashmir, 190006, India.
authors.forename: Naveed Anjum
authors.initials: NA
authors.lastname: Chikan
authors.affiliation: Departments of Biotechnology, University of Kashmir, Srinagar, Kashmir, 190006, India.
authors.forename: Shoiab
authors.initials: S
authors.lastname: Bukhari
authors.affiliation: Department of Animal Biotechnology, College of Veterinary Sciences, Anand Agricultural University, Anand, Gujarat, India, 388 001.
authors.forename: Nadeem
authors.initials: N
authors.lastname: Shabir
authors.affiliation: Departments of Biotechnology, University of Kashmir, Srinagar, Kashmir, 190006, India.
authors.forename: Asif
authors.initials: A
authors.lastname: Amin
authors.affiliation: Department of Clinical Biochemistry, Sher-i- Kashmir Institute of Medical Sciences, Srinagar, Kashmir, 190011, India.
authors.forename: Sheikh
authors.initials: S
authors.lastname: Shafi
authors.affiliation: Departments of Biotechnology, University of Kashmir, Srinagar, Kashmir, 190006, India.
authors.forename: Raies Ahmad
authors.initials: RA
authors.lastname: Qadri
authors.affiliation: Division of Medical Biotechnology, School of Bioscience and Technology, VIT University, Vellore, Tamil Nadu, 632014, India.
authors.forename: Trupti Navin Chandra
authors.initials: TN
authors.lastname: Patel
mesh_terms: D005091:Exons / Q000235:genetics; D006801:Humans; D006860:Hydrogen Bonding; D008958:Models, Molecular; D008969:Molecular Sequence Data; D050505:Mutant Proteins / Q000737:chemistry; D019853:O(6)-Methylguanine-DNA Methyltransferase / Q000737:chemistry*; D017434:Protein Structure, Tertiary; D013274:Stomach Neoplasms / Q000201:enzymology*; D013816:Thermodynamics
chemical_list: D050505:Mutant Proteins; D019853:O(6)-Methylguanine-DNA Methyltransferase