CHAP domain. This domain corresponds to an amidase function. Many of these proteins are involved in cell wall metabolism of bacteria. This domain is found at the N-terminus of Escherichia coli gss, where it functions as a glutathionylspermidine amidase EC:3.5.1.78. This domain is found to be the catalytic domain of PlyCA. CHAP is the amidase domain of bifunctional Escherichia coli glutathionylspermidine synthetase/amidase, and it catalyzes the hydrolysis of Gsp (glutathionylspermidine) into glutathione and spermidine.
PspA/IM30 family. This family includes PspA a protein that suppresses sigma54-dependent transcription. The PspA protein, a negative regulator of the Escherichia coli phage shock psp operon, is produced when virulence factors are exported through secretins in many Gram-negative pathogenic bacteria and its homolog in plants, VIPP1, plays a critical role in thylakoid biogenesis, essential for photosynthesis. Activation of transcription by the enhancer-dependent bacterial sigma(54) containing RNA polymerase occurs through ATP hydrolysis-driven protein conformational changes enabled by activator proteins that belong to the large AAA(+) mechanochemical protein family. It has been shown that PspA directly and specifically acts upon and binds to the AAA(+) domain of the PspF transcription activator.