title: Insight into autoproteolytic activation from the structure of cephalosporin acylase: a protein with two proteolytic chemistries.
abstract: Cephalosporin acylase (CA), a member of the N-terminal nucleophile hydrolase family, is activated through sequential primary and secondary autoproteolytic reactions with the release of a pro segment. We have determined crystal structures of four CA mutants. Two mutants are trapped after the primary cleavage, and the other two undergo secondary cleavage slowly. These structures provide a look at pro-segment conformation during activation in N-terminal nucleophile hydrolases. The highly strained helical pro segment of precursor is transformed into a relaxed loop in the intermediates, suggesting that the relaxation of structural constraints drives the primary cleavage reaction. The secondary autoproteolytic step has been proposed to be intermolecular. However, our analysis provides evidence that CA is processed in two sequential steps of intramolecular autoproteolysis involving two distinct residues in the active site, the first a serine and the second a glutamate.
authors.affiliation: Department of Life Sciences and Biotechnology, School of Life Sciences and Biotechnology, Korea University, Seoul 136-701, Korea.
authors.forename: Jin Kwang
authors.initials: JK
authors.lastname: Kim
authors.forename: In Seok
authors.initials: IS
authors.lastname: Yang
authors.forename: Hye Jeong
authors.initials: HJ
authors.lastname: Shin
authors.forename: Ki Joon
authors.initials: KJ
authors.lastname: Cho
authors.forename: Eui Kyung
authors.initials: EK
authors.lastname: Ryu
authors.forename: Sun Hwa
authors.initials: SH
authors.lastname: Kim
authors.forename: Sung Soo
authors.initials: SS
authors.lastname: Park
authors.forename: Kyung Hyun
authors.initials: KH
authors.lastname: Kim
mesh_terms: D000595:Amino Acid Sequence; D002412:Cations / Q000737:chemistry; D004789:Enzyme Activation; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009154:Mutation / Q000187:drug effects; D010399:Penicillin Amidase / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D017434:Protein Structure, Tertiary; D011549:Pseudomonas / Q000201:enzymology* / Q000235:genetics; D040681:Structural Homology, Protein
chemical_list: D002412:Cations; D010399:Penicillin Amidase