SyrA is a small protein located in the cytoplasmic membrane that lacks an apparent DNA binding domain. SyrA mediates the transcriptional up-regulation of exo genes involved in the biosynthesis of the symbiotic exopolysaccharide succinoglycan. It does this through a mechanism which requires a two component system [1].

1: Sinorhizobium meliloti SyrA mediates the transcriptional regulation of genes involved in lipopolysaccharide sulfation and exopolysaccharide biosynthesis. Keating DH; J Bacteriol. 2007;189:2510-2520. PMID:17209018