The oligomeric structure of human granzyme A is a determinant of its extended substrate specificity.
The cell death-inducing serine protease granzyme A (GzmA) has a unique disulfide-linked quaternary structure. The structure of human GzmA bound to a tripeptide CMK inhibitor, determined at a resolution of 2.4 A, reveals that the oligomeric state contributes to substrate selection by limiting access to the active site for potential macromolecular substrates and inhibitors. Unlike other serine proteases, tetrapeptide substrate preferences do not correlate well with natural substrate cleavage sequences. This suggests that the context of the cleavage sequence within a macromolecular substrate imposes another level of selection not observed with the peptide substrates. Modeling of inhibitors bound to the GzmA active site shows that the dimer also contributes to substrate specificity in a unique manner by extending the active-site cleft. The crystal structure, along with substrate library profiling and mutagenesis, has allowed us to identify and rationally manipulate key components involved in GzmA substrate specificity.
Bell
Jessica K
JK
Department of Pharmaceutical Chemistry, University of California, San Francisco, California 94143, USA.
Goetz
David H
DH
Mahrus
Sami
S
Harris
Jennifer L
JL
Fletterick
Robert J
RJ
Craik
Charles S
CS
D000595:Amino Acid Sequence; D001704:Biopolymers / Q000737:chemistry* / Q000378:metabolism; D019281:Dimerization; D053804:Granzymes; D006801:Humans; D008958:Models, Molecular; D008969:Molecular Sequence Data; D011485:Protein Binding; D020836:Protein Structure, Quaternary; D011994:Recombinant Proteins / Q000737:chemistry / Q000378:metabolism; D017386:Sequence Homology, Amino Acid; D012697:Serine Endopeptidases / Q000737:chemistry* / Q000378:metabolism; D013379:Substrate Specificity
D001704:Biopolymers; D011994:Recombinant Proteins; D053804:Granzymes; D012697:Serine Endopeptidases; C509212:GZMA protein, human