title: Functional and conformational transitions of mevalonate diphosphate decarboxylase from Bacopa monniera.
abstract: Functional and conformational transitions of mevalonate diphosphate decarboxylase (MDD), a key enzyme of mevalonate pathway in isoprenoid biosynthesis, from Bacopa monniera (BmMDD), cloned and overexpressed in Escherichia coli were studied under thermal, chemical and pH-mediated denaturation conditions using fluorescence and Circular dichroism spectroscopy. Native BmMDD is a helix dominant structure with 45% helix and 11% sheets and possesses seven tryptophan residues with two residues exposed on surface, three residues partially exposed and two situated in the interior of the protein. Thermal denaturation of BmMDD causes rapid structural transitions at and above 40°C and transient exposure of hydrophobic residues at 50°C, leading to aggregation of the protein. An acid induced molten globule like structure was observed at pH 4, exhibiting altered but compact secondary structure, distorted tertiary structure and exposed hydrophobic residues. The molten globule displayed different response at higher temperature and similar response to chemical denaturation as compared to the native protein. The surface tryptophans have predominantly positively charged amino acids around them, as indicated by higher KSV for KI as compared to that for CsCl. The native enzyme displayed two different lifetimes, τ1 (1.203±0.036 ns) and τ2 (3.473±0.12 ns) indicating two populations of tryptophan.
authors.affiliation: Plant Tissue Culture Division, National Chemical Laboratory, Pune 411008, India.
authors.forename: Shakeel
authors.initials: S
authors.lastname: Abbassi
authors.affiliation: Plant Tissue Culture Division, National Chemical Laboratory, Pune 411008, India.
authors.forename: Krunal
authors.initials: K
authors.lastname: Patel
authors.affiliation: Plant Tissue Culture Division, National Chemical Laboratory, Pune 411008, India.
authors.forename: Bashir
authors.initials: B
authors.lastname: Khan
authors.affiliation: Division of Biochemical Sciences, National Chemical Laboratory, Pune 411008, India.
authors.forename: Siddharth
authors.initials: S
authors.lastname: Bhosale
authors.affiliation: Division of Biochemical Sciences, National Chemical Laboratory, Pune 411008, India. Electronic address: sm.gaikwad@ncl.res.in.
authors.forename: Sushama
authors.initials: S
authors.lastname: Gaikwad
mesh_terms: D034681:Bacopa / Q000737:chemistry*; D002262:Carboxy-Lyases / Q000737:chemistry*; D002942:Circular Dichroism / Q000379:methods; D005453:Fluorescence; D006863:Hydrogen-Ion Concentration; D011487:Protein Conformation; D011489:Protein Denaturation; D017510:Protein Folding; D014364:Tryptophan / Q000737:chemistry
chemical_list: D014364:Tryptophan; D002262:Carboxy-Lyases; C022503:pyrophosphomevalonate decarboxylase
keywords: Aggregation; CD spectroscopy; Fluorescence quenching; Mevalonate diphosphate decarboxylase; Unfolding