Functional and structural similarity between the X protein of hepatitis B virus and nucleoside diphosphate kinases

• Published in: FEBS letters Vol. 351; no. 3; pp. 423 - 426
• Main Authors: De-Medina, Tali, Shaul, Yosef
• Format: Journal Article
• Language: English
• Published: England Elsevier B.V 12.09.1994
• Subjects: Amino Acid Sequence; Animals; Chromatography, Thin Layer; Electrophoresis, Polyacrylamide Gel; Escherichia coli; Hepatitis B virus; Humans; Molecular Sequence Data; NDPK; Nucleoside-Diphosphate Kinase - chemistry; Nucleoside-Diphosphate Kinase - metabolism; Protein kinase; Protein Kinases - chemistry; Protein Kinases - metabolism; Recombinant Proteins - chemistry; Recombinant Proteins - isolation & purification; Recombinant Proteins - metabolism; Sequence Homology, Amino Acid; Structure-Activity Relationship; Trans-Activators - chemistry; Trans-Activators - isolation & purification; Trans-Activators - metabolism; Transcription; Transcription, Genetic; X protein; Hepatitis B virus; X protein; Transcription; NDPK; Protein kinase
• ISSN: 0014-5793; 1873-3468
• DOI: 10.1016/0014-5793(94)00900-7

One of the four genes encoded by hepatitis B virus (HBV) is the regulatory 17 kDa protein called HBx (or pX). HBx is a transcription transactivator of many cellular and viral regulatory elements. We report here that recombinant HBx supports transcription in vitro and has phosphotransfer enzymatic activity. In the presence of EDTA, a phosphoryl-HBx is formed that releases the phosphate residue upon the addition of Mg 2+. This two-step NTP hydrolysis reaction is characteristic of a group of enzymes termed nucleoside diphosphate kinases (NDPKs). Remarkably, structural similarity between HBx and NDPKs is also evident. Our findings suggest that HBx has evolved from this group of enzymes but acquired additional activities that satisfy the viral needs.