Identification of an extremely thermostable enzyme with dual sugar-1-phosphate nucleotidylyltransferase activities from an acidothermophilic archaeon, Sulfolobus tokodaii strain 7.
ABSTRACT L-rhamnose is an essential component of the cell wall and plays roles in mediating virulence and adhesion to host tissues in many microorganisms. Glucose-1-phosphate thymidylyltransferase (RmlA, EC 18.104.22.168) catalyzes the first reaction of the four-step pathway of L-rhamnose biosynthesis, producing dTDP-D-glucose from dTTP and glucose-1-phosphate. Three RmlA homologues of varying size have been identified in the genome of a thermophilic archaeon, Sulfolobus tokodaii strain 7. In this study, we report the heterologous expression of the largest homologue (a 401 residue-long ST0452 protein) and characterization of its thermostable activity. RmlA enzymatic activity of this protein was detected from 65 to 100 degrees C, with a half-life of 60 min at 95 degrees C and 180 min at 80 degrees C. Analysis of a deletion mutant lacking the 170-residue C-terminal domain indicated that this region has an important role in the thermostability and activity of the protein. Analyses of substrate specificity indicated that the enzymatic activity of the full-length protein is capable of utilizing alpha-D-glucose-1-phosphate and N-acetyl-D-glucosamine-1-phosphate but not alpha-D-glucosamine-1-phosphate. However, the protein is capable of utilizing all four deoxyribonucleoside triphosphates and UTP. Thus, the ST0452 protein is an enzyme containing both glucose-1-phosphate thymidylyltransferase and N-acetyl-D-glucosamine-1-phosphate uridylyltransferase activities. This is the first report of a thermostable enzyme with dual sugar-1-phosphate nucleotidylyltransferase activities.
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ABSTRACT: Two similar genes, dnmL and rmbA in Streptomyces peucetius, which encode for glucose-1-phosphate (G-1-P) thymidylyltransferases were expressed in Escherichia coli under similar conditions. While RmbA was expressed in soluble form, DnmL was found as insoluble aggregates in inclusion bodies. The difference in expression of these similar proteins led to investigate into the amino acid sequences of these proteins by sequence alignment, hydrophobicity scale and homology modeling. These analyses showed that the two proteins are different only in the C-terminal sequences. Deletion of C-terminal sequence of DnmL increased the expression level of truncated DnmL. Substitution of C-terminal sequence of DnmL with RmbA also expressed the recombinant protein in soluble form. Finally, mutation of six amino acids in DnmL rendered the protein expressed in soluble form. These results suggested that the soluble expression of the thymidylyltransferases lies in the C-terminal sequences. In conclusion, these methods of protein engineering will be a rational tool for enhancing solubility of proteins expressed in E.coli.Protein Engineering Design and Selection 02/2012; 25(4):179-87. · 2.59 Impact Factor
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ABSTRACT: A 401-residue-long protein, ST0452, has been identified from a thermophilic archaeon, Sulfolobus tokodaii strain 7, as a glucose-1-phosphate thymidylyltransferase (Glc-1-P TTase) homolog with a 170-residue-long extra C-terminus portion. Functional analyses of the ST0452 protein have confirmed that the protein possessed dual sugar-1-phosphate nucleotidylyltransferase (sugar-1-P NTase) activities. The 24 repeats of a signature motif sequence which has been found in bacterial acetyltransferases, (L/I/V)-(G/A/E/D)-XX-(S/T/A/V)-X, were detected at the C terminus of the ST0452 protein. This observation prompted our group to investigate the acetyltransferase activity of the ST0452 protein. Detection of the release of coenzyme A (CoA) from acetyl-CoA and the production of UDP-N-acetyl-d-glucosamine (UDP-GlcNAc) from glucosamine-1-phosphate (GlcN-1-P) and UTP in the presence of the ST0452 protein revealed that this protein possesses the GlcN-1-P-specific acetyltransferase activity. In addition, analyses of substrate specificity showed that acetyltransferase activity of the ST0452 protein is capable of catalyzing the change of galactosamine-1-phosphate (GalN-1-P) to N-acetyl-d-galactosamine-1-phosphate (GalNAc-1-P) as well as GlcN-1-P and that its sugar-1-P NTase activity is capable of producing UDP-GalNAc from GalNAc-1-P and UTP. This is the first report of a thermostable bifunctional enzyme with GalN-1-P acetyltransferase and GalNAc-1-P uridyltransferase activities. The observation reveals that the bacteria-type UDP-GlcNAc biosynthetic pathway from fructose-6-phospate is utilized in this archaeon and represents a novel biosynthetic pathway for producing UDP-GalNAc from GalN-1-P in this microorganism.Journal of bacteriology 07/2010; 192(13):3287-93. · 3.94 Impact Factor
- 01/2012; , ISBN: 978-953-307-820-5