title: Crystal structure of a carbohydrate induced homodimer of phospholipase A2 from Bungarus caeruleus at 2.1A resolution.
abstract: This is the first crystal structure of a carbohydrate induced dimer of phospholipase A(2) (PLA(2)). This is an endogenous complex formed between two PLA(2) molecules and two mannoses. It was isolated from Krait venom (Bungarus caeruleus) and crystallized as such. The complete amino acid sequence of PLA(2) was determined using cDNA method. Three-dimensional structure of the complex has been solved with molecular replacement method and refined to a final R-factor of 0.192 for all the data in the resolution range 20.0-2.1A. The presence of mannose molecules in the protein crystals was confirmed using dinitrosalicylic acid test and the molecular weight of the dimer was verified with MALDI-TOF. As indicated by dynamic light scattering and analytical ultracentrifugation the dimer was also stable in solution. The good quality non-protein electron density at the interface of two PLA(2) molecules enabled us to model two mannoses. The mannoses are involved extensively in interactions with protein atoms of both PLA(2) molecules. Some of the critical amino acid residues such as Asp 49 and Tyr 31, which are part of the substrate-binding site, are found facing the interface and interacting with mannoses. The structure of the complex clearly shows that the dimerization is caused by mannoses and it results in the loss of enzymatic activity.
authors.affiliation: Department of Biophysics, All India Institute of Medical Sciences, New Delhi 110 029, India.
authors.forename: Garima
authors.initials: G
authors.lastname: Singh
authors.forename: S
authors.initials: S
authors.lastname: Gourinath
authors.forename: K
authors.initials: K
authors.lastname: Sarvanan
authors.forename: Sujata
authors.initials: S
authors.lastname: Sharma
authors.forename: S
authors.initials: S
authors.lastname: Bhanumathi
authors.forename: Ch
authors.initials: Ch
authors.lastname: Betzel
authors.forename: Savita
authors.initials: S
authors.lastname: Yadav
authors.forename: A
authors.initials: A
authors.lastname: Srinivasan
authors.forename: T P
authors.initials: TP
authors.lastname: Singh
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D017838:Bungarus; D018360:Crystallography, X-Ray; D019281:Dimerization; D008358:Mannose / Q000737:chemistry*; D008958:Models, Molecular; D008969:Molecular Sequence Data; D010741:Phospholipases A / Q000737:chemistry* / Q000235:genetics; D054467:Phospholipases A2; D020836:Protein Structure, Quaternary; D016415:Sequence Alignment; D012910:Snake Venoms / Q000737:chemistry*; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization
chemical_list: D012910:Snake Venoms; D010741:Phospholipases A; D054467:Phospholipases A2; D008358:Mannose