Summary auto-generated
Researchers screened 152 Thermus isolates from hot springs across four continents for the restriction endonuclease TaqI (recognizing T/CGA). Twenty-seven isolates containing TaqI isoschizomers were identified, with six selected from diverse geographic origins—New Zealand, Iceland, USA, Japan, Portugal, and the Azores—representing five Thermus species: T. aquaticus, T. filiformis, T. thermophilus, T. scotoductus, and T. brockianus. The TaqI isoschizomers were partially purified and compared biochemically. Despite recognizing the same DNA sequence, these isoschizomers exhibited striking differences in their properties: they required varying magnesium ion concentrations (1.0 to 2.5 mM), had different isoelectric points, showed different subunit molecular masses (29–31 kDa, with one variant at 25 kDa), and demonstrated a wide range of thermal stabilities (68–84°C). All isoschizomers required similar pH optima (9.5–10.0) and had identical sodium ion requirements. The most thermostable variant (B) from New Zealand was more stable than the prototype TaqI from T. aquaticus YT1, suggesting these geographically diverse enzymes could be engineered for improved thermal stability.
Key findings
- Twenty-seven TaqI isoschizomers were identified from Thermus isolates collected from hot springs on four continents (New Zealand, Iceland, USA, Japan, Portugal, Azores)
- The six TaqI isoschizomers examined required different magnesium ion concentrations (1.0–2.5 mM) and had variable thermal stabilities ranging from 68°C to 84°C
- Despite being isoschizomers with identical recognition sequences, these enzymes differed significantly in subunit molecular masses (29–31 kDa, one at 25 kDa) and isoelectric points
- The New Zealand isolate (isoschizomer B) was more thermostable than the prototype TaqI, retaining full activity at 84°C for 5 minutes
- All isoschizomers showed similar pH optima (9.5–10.0) and identical sodium ion requirements, but different responses to high magnesium concentrations
This summary was generated automatically from the article PDF and is not part of the original publication. Refer to the PDF for the authoritative text.
Abstract
One-hundred-and-fifty-two isolates of the genus Thermus, collected from hot springs on four continents, were screened for evidence of the presence of the thermophilic Type II restriction endonuclease TaqI (T/CGA). The presence of isoschizomers of TaqI in 27 of the isolates, originating from hot springs in New Zealand, Iceland, USA, Japan, mainland Portugal and the island of Sao Miguel in the Azores, is reported. Six of the TaqI-containing isolates from diverse geographical locations, identified by means of DNA/DNA homology and 16S rRNA sequence alignment as belonging to the Thermus species T. aquaticus, T. filiformis, T. thermophilus, T. scotoductus and T. brockianus, were selected for comparative studies. The TaqI isoschizomers from each of the six isolates were partially purified. They differed in their magnesium ion requirements, isoelectric points, subunit molecular masses and thermal stability.