Substrates and inhibitors of human T-cell leukemia virus type I protease.

Abstract

HTLV-I is an oncogenic retrovirus that is associated with adult T-cell leukemia. HTLV-I protease and HTLV-I protease fused to a deca-histidine containing leader peptide (His-protease) have been cloned, expressed, and purified. The refolded proteases were active and exhibited nearly identical enzymatic activities. To begin to characterize the specificity of HTLV-I, we measured protease cleavage of peptide substrates and inhibition by protease inhibitors. HTLV-I protease cleavage of a peptide representing the HTLV-I retroviral processing site P19/24 (APQVLPVMHPHG) yielded Km and kcat values of 470 microM and 0.184 s-1 while cleavage of a peptide representing the processing site P24/15 (KTKVLVVQPK) yielded Km and kcat values of 310 microM and 0.0060 s-1. When the P1' proline of P19/24 was replaced with p-nitro-phenylalanine (Nph), the ability of HTLV-I protease to cleave the substrate (APQVLNphVMHPL) was improved. Inhibition of HTLV-I protease and His-protease by a series of protease inhibitors was also tested. It was found that the Ki values for inhibition of HTLV-I protease and His-protease by a series of pepsin inhibitors ranged from 7 nM to 10 microM, while the Ki values of a series of HIV-1 protease inhibitors ranged from 6 nM to 127 microM. In comparison, the Ki values for inhibition of pepsin by the pepsin inhibitors ranged from 0.72 to 19.2 nM, and the Ki values for inhibition of HIV-1 protease by the HIV protease inhibitors ranged from 0.24 nM to 1.0 microM. The data suggested that the substrate binding site of HTLV-I protease is different from the substrate binding sites of pepsin and HIV-1 protease, and that currently employed HIV-1 protease inhibitors would not be effective for the treatment of HTLV-I infections.

• Authors: Y S Ding, D H Rich, R A Ikeda
• Journal: Biochemistry (Biochemistry) Vol. 37 Issue 50 Pg. 17514-8 (Dec 15 1998) ISSN: 0006-2960 [Print] United States
• PMID: 9860866 (Publication Type: Comparative Study, Journal Article)

Chemical References

• HIV Protease Inhibitors
• MES13-099
• Oligopeptides
• Protease Inhibitors
• Protein Sorting Signals
• Pyrones
• Recombinant Fusion Proteins
• JG 365
• Histidine
• Aspartic Acid Endopeptidases
• HTLV-1 protease

Topics

• Amino Acid Sequence
• Aspartic Acid Endopeptidases (antagonists & inhibitors, genetics, metabolism)
• Enzyme Activation
• HIV Protease Inhibitors (pharmacology)
• Histidine (genetics)
• Human T-lymphotropic virus 1 (enzymology)
• Humans
• Molecular Sequence Data
• Oligopeptides (pharmacology)
• Protease Inhibitors (metabolism, pharmacology)
• Protein Sorting Signals (genetics)
• Pyrones (pharmacology)
• Recombinant Fusion Proteins (antagonists & inhibitors, metabolism)
• Substrate Specificity