title: Amino acid substitution on Beta1 and alphaF of Cyt2Aa2 affects molecular interaction of protoxin.
abstract: Cyt2Aa2 is a mosquito-larvicidal protein produced as a 29 kDa crystalline protoxin from Bacillus thuringiensis subsp. darmstadiensis. To become an active toxin, proteolytic processing is required to remove amino acids from its N- and C-termini. This study aims to investigate the functional role of amino acid residues on the N-terminal Beta1 and C-terminal alphaF of Cyt2Aa2 protoxin. Mutant protoxins were constructed, characterized and compared to the wild type Cyt2Aa2. Protein expression data and SDS-PAGE analysis revealed that substitution at leucine- 33 (L33) of Beta1 has a critical effect on dimer formation and structural stability against proteases. In addition, amino acids N230 and I233-F237 around the C-terminus alphaF demonstrated a crucial role in protecting the protoxin from proteolytic digestion. These results suggested that Beta1 and alphaF on the Nand C-terminal ends of Cyt2Aa2 protoxin play an important role in the molecular interaction and in maintaining the structural stability of the protoxin.
authors.affiliation: Institute of Molecular Biosciences, Mahidol University, Salaya, Nakhon Pathom, Thailand.
authors.forename: Siriya
authors.initials: S
authors.lastname: Thammachat
authors.forename: Nuanwan
authors.initials: N
authors.lastname: Pungtanom
authors.forename: Somruathai
authors.initials: S
authors.lastname: Kidsanguan
authors.forename: Wanwarang
authors.initials: W
authors.lastname: Pathaichindachote
authors.forename: Boonhiang
authors.initials: B
authors.lastname: Promdonkoy
authors.forename: Chartchai
authors.initials: C
authors.lastname: Krittanai
mesh_terms: D000595:Amino Acid Sequence; D019943:Amino Acid Substitution; D001427:Bacterial Toxins / Q000737:chemistry* / Q000235:genetics; D019281:Dimerization; D004591:Electrophoresis, Polyacrylamide Gel; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D013050:Spectrometry, Fluorescence
chemical_list: D001427:Bacterial Toxins