title: Structure of granzyme C reveals an unusual mechanism of protease autoinhibition.
abstract: Proteases act in important homeostatic pathways and are tightly regulated. Here, we report an unusual structural mechanism of regulation observed by the 2.5-A X-ray crystal structure of the serine protease, granzyme C. Although the active-site triad residues adopt canonical conformations, the oxyanion hole is improperly formed, and access to the primary specificity (S1) pocket is blocked through a reversible rearrangement involving Phe-191. Specifically, a register shift in the 190-strand preceding the active-site serine leads to Phe-191 filling the S1 pocket. Mutation of a unique Glu-Glu motif at positions 192-193 unlocks the enzyme, which displays chymase activity, and proteomic analysis confirms that activity of the wild-type protease can be released through interactions with an appropriate substrate. The 2.5-A structure of the unlocked enzyme reveals unprecedented flexibility in the 190-strand preceding the active-site serine that results in Phe-191 vacating the S1 pocket. Overall, these observations describe a broadly applicable mechanism of protease regulation that cannot be predicted by template-based modeling or bioinformatic approaches alone.
authors.affiliation: Department of Biochemistry and Molecular Biology, Monash University, Clayton 3800, Australia.
authors.forename: Dion
authors.initials: D
authors.lastname: Kaiserman
authors.forename: Ashley M
authors.initials: AM
authors.lastname: Buckle
authors.forename: Petra
authors.initials: P
authors.lastname: Van Damme
authors.forename: James A
authors.initials: JA
authors.lastname: Irving
authors.forename: Ruby H P
authors.initials: RH
authors.lastname: Law
authors.forename: Antony Y
authors.initials: AY
authors.lastname: Matthews
authors.forename: Tanya
authors.initials: T
authors.lastname: Bashtannyk-Puhalovich
authors.forename: Chris
authors.initials: C
authors.lastname: Langendorf
authors.forename: Philip
authors.initials: P
authors.lastname: Thompson
authors.forename: Joël
authors.initials: J
authors.lastname: Vandekerckhove
authors.forename: Kris
authors.initials: K
authors.lastname: Gevaert
authors.forename: James C
authors.initials: JC
authors.lastname: Whisstock
authors.forename: Phillip I
authors.initials: PI
authors.lastname: Bird
mesh_terms: D000596:Amino Acids; D000818:Animals; D020134:Catalytic Domain; D018360:Crystallography, X-Ray; D053804:Granzymes / Q000737:chemistry*; D011487:Protein Conformation; D012377:Rodentia; D012697:Serine Endopeptidases / Q000378:metabolism*; D015842:Serine Proteinase Inhibitors
chemical_list: D000596:Amino Acids; D015842:Serine Proteinase Inhibitors; D053804:Granzymes; D012697:Serine Endopeptidases