Forms an equimolar complex with the RNA polymerase holoenzyme (RNAP) but not with the core enzyme. It is synthesized predominantly when cells are exposed to amino acid starvation, at which time it accounts for over 50% of the total protein synthesized. It is involved in the transition from P1 early to P1 late gene expression. Rnk and SspA can functionally replace P.aeruginosa alginate regulatory gene algR2. By amino acid starvation. Belongs to the GST superfamily. HSP26 family.