Sequence and expression of the gene for Clostridium cylindrosporum

Sau3 A and Hind III restriction fragments of Clostridium cylindrosporum genomic DNA were used to isolate clones containing 80% of the N¹⁰‐H₄folate synthetase gene in a 5′ fragment and the remaining 20% of the gene in the 3′ fragment. These fragments were joined at a common SnaB I restriction site and expressed in Escherichia coli at a level equivalent to what is normally found in C. cylindrosporum. Sequence comparisons show a large degree of homology with genes from two other clostridial species, including a thermophile. Certain conserved sequences found in the three clostridial proteins and in the N¹⁰‐H₄folate synthetase portion of eukaryotic Cl‐H₄folate synthases may represent consensus sequences for nucleotide and H₄folate binding.