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Human and murine granzyme B exhibit divergent substrate preferences.

ABSTRACT: The cytotoxic lymphocyte protease granzyme B (GzmB) can promote apoptosis through direct processing and activation of members of the caspase family. GzmB can also cleave the BH3-only protein, BID, to promote caspase-independent mitochondrial permeabilization. Although human and mouse forms of GzmB exhibit extensive homology, these proteases diverge at residues predicted to influence substrate binding. We show that human and mouse GzmB exhibit radical differences in their ability to cleave BID, as well as several other key substrates, such as ICAD and caspase-8. Moreover, pharmacological inhibition of caspases clonogenically rescued human and mouse target cells from apoptosis initiated by mouse GzmB, but failed to do so in response to human GzmB. These data demonstrate that human and murine GzmB are distinct enzymes with different substrate preferences. Our observations also illustrate how subtle differences in enzyme structure can radically affect substrate selection.

SUBMITTER: Cullen SP

PROVIDER: S-EPMC2063979 | biostudies-literature | 2007 Feb

REPOSITORIES: biostudies-literature

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Human and murine granzyme B exhibit divergent substrate preferences.

Cullen Sean P SP Adrain Colin C Lüthi Alexander U AU Duriez Patrick J PJ Martin Seamus J SJ

The Journal of cell biology 20070205 4

The cytotoxic lymphocyte protease granzyme B (GzmB) can promote apoptosis through direct processing and activation of members of the caspase family. GzmB can also cleave the BH3-only protein, BID, to promote caspase-independent mitochondrial permeabilization. Although human and mouse forms of GzmB exhibit extensive homology, these proteases diverge at residues predicted to influence substrate binding. We show that human and mouse GzmB exhibit radical differences in their ability to cleave BID, a ...[more]

PMID: 17283187

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Project description:The DNA glycosylases that remove oxidized DNA bases fall into two general families: the Fpg/Nei family and the Nth superfamily. Based on protein sequence alignments, we identified four putative Fpg/Nei family members, as well as a putative Nth protein in Mycobacterium tuberculosis H37Rv. All four Fpg/Nei proteins were successfully overexpressed using a bicistronic vector created in our laboratory. The MtuNth protein was also overexpressed in soluble form. The substrate specificities of the purified enzymes were characterized in vitro with oligodeoxynucleotide substrates containing single lesions. Some were further characterized by gas chromatography/mass spectrometry (GC/MS) analysis of products released from gamma-irradiated DNA. MtuFpg1 has substrate specificity similar to that of EcoFpg. Both EcoFpg and MtuFpg1 are more efficient at removing spiroiminodihydantoin (Sp) than 7,8-dihydro-8-oxoguanine (8-oxoG). However, MtuFpg1 shows a substantially increased opposite base discrimination compared to EcoFpg. MtuFpg2 contains only the C-terminal domain of an Fpg protein and has no detectable DNA binding activity or DNA glycosylase/lyase activity and thus appears to be a pseudogene. MtuNei1 recognizes oxidized pyrimidines on both double-stranded and single-stranded DNA and exhibits uracil DNA glycosylase activity. MtuNth recognizes a variety of oxidized bases, including urea, 5,6-dihydrouracil (DHU), 5-hydroxyuracil (5-OHU), 5-hydroxycytosine (5-OHC) and methylhydantoin (MeHyd). Both MtuNei1 and MtuNth excise thymine glycol (Tg); however, MtuNei1 strongly prefers the (5R) isomers, whereas MtuNth recognizes only the (5S) isomers. MtuNei2 did not demonstrate activity in vitro as a recombinant protein, but like MtuNei1 when expressed in Escherichia coli, it decreased the spontaneous mutation frequency of both the fpg mutY nei triple and nei nth double mutants, suggesting that MtuNei2 is functionally active in vivo recognizing both guanine and cytosine oxidation products. The kinetic parameters of the MtuFpg1, MtuNei1 and MtuNth proteins on selected substrates were also determined and compared to those of their E. coli homologs.

Dataset Information

Human and murine granzyme B exhibit divergent substrate preferences.

Publications

Human and murine granzyme B exhibit divergent substrate preferences.

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