Sequence and characterization of an Ehrlichia chaffeensis gene encoding 314 amino acids highly homologous to the NAD A enzyme

DNA sequence analysis of the nadA gene of Ehrlichia chaffeensis revealed a 942 bp open reading frame with the capacity to encode 314 amino acids. The amino acid sequence of the E. chaffeensis quinolinate synthetase A (NAD/A) has 53.6% identity and 82% similarity to the NAD A of the cyanelle of Cyanophora paradoxa. Portions of the homologous genes of E. canis and E. muris were also sequenced. The amino acid sequences of the NAD A of E. canis and E. muris have 89.2% and 93.2% homology, respectively, to the NAD A of E. chaffeensis. We propose that the nadA gene may be an excellent candidate for a genetic tool for the phylogenetic study of ehrlichiae.