Protein kinase B from Giardia intestinalis.
A novel serine/threonine protein kinase from Giardia intestinalis (GiPKB) was isolated by a combination of PCR techniques. Analysis of the GiPKB sequence indicated that the encoded protein appears to be a member of a novel subgroup of serine/threonine protein kinases known as protein kinase B. Reverse transcription PCR and Northern hybridization showed that the transcription of GiPKB is developmentally regulated. The GiPKB was expressed as a recombinant protein, which was characterized and shown to have a protein kinase activity. The preferred substrate for the GiPKB was histone H1, while histone H2A, GSK3 peptide, GS peptide, and Kemptide were phosphorylated at about 96, 73, 51, and 40% of the activity with histone H1, respectively. Neither cAMP, Ca(2+), nor Ca(2+)/calmodulin stimulated the enzyme activity. The GiPKB utilized ATP rather than GTP as a phosphate donor with an apparent K(m) of 20 microM. The identification and characterization of this differentially and constitutively expressed GiPKB should allow further analysis of the regulation and signal transduction pathways in Giardia.
Kim
Kyu-Tae
KT
School of Biotechnology and Biomolecular Sciences, University of New South Wales, Sydney 2052, Australia. kkim29@jhmi.edu
Mok
Myth T S
MT
Edwards
Michael R
MR
D000595:Amino Acid Sequence; D000818:Animals; D016829:Giardia lamblia / Q000235:genetics* / Q000378:metabolism*; D008969:Molecular Sequence Data; D008970:Molecular Weight; D017346:Protein Serine-Threonine Kinases / Q000032:analysis / Q000737:chemistry*; D011518:Proto-Oncogene Proteins / Q000032:analysis / Q000737:chemistry*; D051057:Proto-Oncogene Proteins c-akt; D011994:Recombinant Proteins / Q000032:analysis / Q000737:chemistry; D017386:Sequence Homology, Amino Acid
D011518:Proto-Oncogene Proteins; D011994:Recombinant Proteins; D017346:Protein Serine-Threonine Kinases; D051057:Proto-Oncogene Proteins c-akt