The recently identified fla operon of Treponema pallidum contains several genes that encode motility-related proteins. We have determined the nucleotide sequences of three genes, designated flhA, flhF, and orf304, that are located immediately downstream of the flhB gene in the fla operon. The flhA gene encodes a 707-amino acid protein that contains five putative membrane spanning domains. FlhA has strong homology with members of a family of proteins that are involved in flagellar biogenesis and regulation/secretion of virulence-related proteins. The flhF gene encodes a 437-amino acid protein that contains three consensus elements that are characteristic of a GTP-binding domain. The orf304 gene encodes a 304-amino acid protein that contains a consensus ATP-binding motif. The order of the flhA, flhF, and orf304 genes is identical to that of corresponding genes in the Bacillus subtilis che/fla operon. Due to the location of the flhA, flhF and orf304 genes in the T. pallidum fla operon, we hypothesize that the FlhA, FlhF, and Orf304 proteins are involved in the biogenesis/assembly of treponemal periplasmic flagella.