Crystal structure of human bleomycin hydrolase, a self-compartmentalizing cysteine protease.
BACKGROUND
Bleomycin hydrolase (BH) is a cysteine protease that is found in all tissues in mammals as well as in many other eukaryotes and prokaryotes. Although its conserved cellular function is as yet unknown, human bleomycin hydrolase (hBH) has clinical significance in that it is thought to be the major cause of tumor cell resistance to bleomycin chemotherapy. In addition, it has been reported that an allelic variant of hBH is genetically linked to Alzheimer's disease.


RESULTS
We have determined the crystal structures of wild-type hBH and of a mutant form of the enzyme. The overall structure is very similar to that of the previously determined yeast homolog, however, there is a striking difference in the charge distribution. The central channel, which has a strong positive electrostatic potential in the yeast protein, is slightly negative in hBH. We have determined that hBH does not have the DNA-binding activity of the yeast protein and that the enzyme is localized to the cytoplasm.


CONCLUSIONS
The difference in charge distribution between the yeast and human BH enzymes is most likely responsible for the difference in DNA-binding activity. Nevertheless, the C-terminal autoprocessing activity and the role of the C terminus as a determinant for peptidase activity are conserved between the yeast and human forms. The structure of hBH suggests that the putative Alzheimer's disease linked variation does not directly alter the intrinsic peptidase activity. Rather, the position of the mutation suggests that it could affect interactions with another protein, which may modulate peptidase activity through repositioning of the C terminus.
O'Farrell
P A
PA
WM Keck Structural Biology Laboratory, Cold Spring Harbor Laboratory, NY 11724, USA.
Gonzalez
F
F
Zheng
W
W
Johnston
S A
SA
Joshua-Tor
L
L
D000544:Alzheimer Disease / Q000201:enzymology; D000595:Amino Acid Sequence; D000970:Antineoplastic Agents / Q000378:metabolism / Q000627:therapeutic use; D001665:Binding Sites; D001761:Bleomycin / Q000378:metabolism / Q000627:therapeutic use; D018360:Crystallography, X-Ray; D003546:Cysteine Endopeptidases / Q000737:chemistry* / Q000235:genetics; D004268:DNA-Binding Proteins / Q000737:chemistry; D004351:Drug Resistance; D005455:Fluorescent Antibody Technique; D005656:Fungal Proteins / Q000737:chemistry; D006801:Humans; D006860:Hydrogen Bonding; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009154:Mutation / Q000235:genetics; D011487:Protein Conformation; D011994:Recombinant Proteins / Q000737:chemistry; D055672:Static Electricity
D000970:Antineoplastic Agents; D004268:DNA-Binding Proteins; D005656:Fungal Proteins; D011994:Recombinant Proteins; D001761:Bleomycin; D003546:Cysteine Endopeptidases; C031262:bleomycin hydrolase