Identification, structure, and phylogenetic relationships of a mitogen-activated protein kinase homologue from the parasitic protist Entamoeba histolytica.
A gene encoding mitogen-activated protein kinase (MAPK) from the human enteric parasite, Entamoeba histolytica has been identified. Sequence analyses of the polymerase chain reaction (PCR) and reverse transcription PCR (RT-PCR) products reveal that the EhMAPK gene is intronless and encodes a protein of 352 amino acids. EhMAPK shows significant homology with other MAPKs and contains the 11 subdomains including the invariant residues characteristic of serine/threonine protein kinases. The MAPK signature residues and motifs are also present in EhMAPK. The atomic model of EhMAPK built with rat ERK2 as template exhibits the conservation of all major secondary structural features. However, a deletion in close proximity to the dual phosphorylation/activation site is of particular interest as it may have functional implications. Phylogenetic analysis indicates that EhMAPK is tightly clustered with Giardia intestinalis ERK2 and Dictyostelium discoideum ERK2. Detailed sequence analysis and phylogenetic study aided us to postulate that EhMAPK belongs to the extracellular signal-regulated kinase (ERK) family. Although EhMAPK bears good homology and phylogenetic closeness with human ERK8 and rat ERK7, sequence analysis indicates that they may be functionally different. The significant differences such as the deletions in the vicinity of the phosphorylation lip, variations in the P+1 specificity pocket, presence of additional acidic amino acids in the common docking domain provide a ground for postulations that activators and substrates for EhMAPK may be to some extent divergent from that of the ERKs of the mammalian host. Although functional characterization of EhMAPK remains to be done, this is the first study of any member of the MAPK signaling system in this organism.
Ray
Doel
D
Crystallography and Molecular Biology Division, Saha Institute of Nuclear Physics, 1/AF Bidhan nagar, Kolkata-700064, India.
Dutta
Suman
S
Banerjee
Sampali
S
Banerjee
Rahul
R
Raha
Sanghamitra
S
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D017931:DNA Primers; D004748:Entamoeba histolytica / Q000201:enzymology*; D020928:Mitogen-Activated Protein Kinases / Q000737:chemistry* / Q000235:genetics; D008958:Models, Molecular; D008969:Molecular Sequence Data; D010802:Phylogeny; D020133:Reverse Transcriptase Polymerase Chain Reaction; D017386:Sequence Homology, Amino Acid
D017931:DNA Primers; D020928:Mitogen-Activated Protein Kinases