The adenylosuccinate synthetase from the hyperthermophilic archaeon Pyrococcus species displays unusual structural features.

The first example of a hyperthermophilic adenylosuccinate synthetase is reported, which is an enzyme that must maintain its folded structure at temperatures as high as 102 degrees C. The amino acid sequence of this key enzyme has been determined after cloning and sequencing the purA-like gene from the archaeal Pyrococcus sp. strain ST700.

A putative SOS repair gene (dinF-like) in a hyperthermophilic archaeon.

The hyperthermophilic archaeon, Pyrococcus (strain IFREMER AL585), contains an ORF that encodes a polypeptide with a high similarity to the Escherichia coli dinF (DNA damage-inducible) gene product. The conservation of this protein between Archaea and Bacteria suggests that a SOS repair system might operate in Archaea.

Functional analysis of the two homologous psbA gene copies in Synechocystis PCC 6714 and PCC 6803.

The cyanobacteria Synechocystis 6803 and 6714 contain three genes (psbA) coding for the D1 protein. This protein is an essential subunit of photosystem II (PSII) and is the target for herbicides. We have used herbicide-resistant mutants to study the role of the two homologous copies of the psbA genes in both strains (the third copy is not expressed).