14 research outputs found
A unique DNase activity shares the active site with ATPase activity of the RecA/Rad51 homologue (Pk-REC) from a hyperthermophilic archaeon
AbstractA RecA/Rad51 homologue from Pyrococcus kodakaraensis KOD1 (Pk-REC) is the smallest protein among various RecA/Rad51 homologues. Nevertheless, Pk-Rec is a super multifunctional protein and shows a deoxyribonuclease activity. This deoxyribonuclease activity was inhibited by 3 mM or more ATP, suggesting that the catalytic centers of the ATPase and deoxyribonuclease activities are overlapped. To examine whether these two enzymatic activities share the same active site, a number of site-directed mutations were introduced into Pk-REC and the ATPase and deoxyribonuclease activities of the mutant proteins were determined. The mutant enzyme in which double mutations Lys-33 to Ala and Thr-34 to Ala were introduced, fully lost both of these activities, indicating that Lys-33 and/or Thr-34 are important for both ATPase and deoxyribonuclease activities. The mutation of Asp-112 to Ala slightly and almost equally reduced both ATPase and deoxyribonuclease activities. In addition, the mutation of Glu-54 to Gln did not seriously affect the ATPase, deoxyribonuclease, and UV tolerant activities. These results strongly suggest that the active sites of the ATPase and deoxyribonuclease activities of Pk-REC are common. It is noted that unlike Glu-96 in Escherichia coli RecA, which has been proposed to be a catalytic residue for the ATPase activity, the corresponding residual Glu-54 in Pk-REC is not involved in the catalytic function of the protein
Nanosizing of polymeric particles by suppressing growth via heterocoagulation using a 3D micro-network reactor
Description of Thermococcus kodakaraensis sp. nov., a well studied hyperthermophilic archaeon previously reported as Pyrococcus sp. KOD1
A hyperthermophilic archaeal strain, KOD1, isolated from a solfatara
on Kodakara Island, Japan, has previously been reported as
Pyrococcus sp. KOD1. However, a detailed phylogenetic
tree, made possible by the recent accumulation of 16S rRNA sequences
of various species in the order Thermococcales, indicated that strain
KOD1 is a member of the genus Thermococcus. We
performed DNA–DNA hybridization tests against species that
displayed high similarity in terms of 16S ribosomal DNA sequences,
including Thermococcus peptonophilus and
Thermococcus stetteri. Hybridization results and
differences in growth characteristics and substrate utilization
differentiated strain KOD1 from T. peptonophilus and
T. stetteri at the species level. Our results
indicate that strain KOD1 represents a new species of
Thermococcus, which we designate as
Thermococcus kodakaraensis KOD1 sp. nov