Crystal structure of cockroach allergen Bla g 2, an unusual zinc binding aspartic protease with a novel mode of self-inhibition.
The crystal structure of Bla g 2 was solved in order to investigate the structural basis for the allergenic properties of this unusual protein. This is the first structure of an aspartic protease in which conserved glycine residues, in two canonical DTG triads, are substituted by different amino acid residues. Another unprecedented feature revealed by the structure is the single phenylalanine residue insertion on the tip of the flap, with the side-chain occupying the S1 binding pocket. This and other important amino acid substitutions in the active site region of Bla g 2 modify the interactions in the vicinity of the catalytic aspartate residues, increasing the distance between them to approximately 4A and establishing unique direct contacts between the flap and the catalytic residues. We attribute the absence of substantial catalytic activity in Bla g 2 to these unusual features of the active site. Five disulfide bridges and a Zn-binding site confer stability to the protein, which may contribute to sensitization at lower levels of exposure than other allergens.
Gustchina
Alla
A
Macromolecular Crystallography Laboratory, National Cancer Institute, Frederick, MD 21702, USA. alla@ncifcrf.gov
Li
Mi
M
Wünschmann
Sabina
S
Chapman
Martin D
MD
Pomés
Anna
A
Wlodawer
Alexander
A
D000595:Amino Acid Sequence; D000818:Animals; D016282:Aspartic Acid Endopeptidases / Q000037:antagonists & inhibitors* / Q000737:chemistry* / Q000378:metabolism; D001665:Binding Sites; D003058:Cockroaches / Q000201:enzymology*; D018360:Crystallography, X-Ray; D006801:Humans; D008958:Models, Molecular; D008969:Molecular Sequence Data; D017510:Protein Folding; D017434:Protein Structure, Tertiary; D016415:Sequence Alignment; D040681:Structural Homology, Protein; D015032:Zinc / Q000378:metabolism*
D016282:Aspartic Acid Endopeptidases; C094699:allergen Bla g 2; D015032:Zinc