CPS operon

The capsule biosynthesis, or CPS operon, is a section of the genome present in some Escherichia coli, of which regulates the production of polysaccharides making up the bacterial capsule.^[1] These polysaccharides help protect the bacteria from harsh environments, toxic chemicals, and bacteriophages.

The CPS operon contains genes which code for the following proteins:

Wza - a lipoprotein which may form a channel in the bacterial outer membrane.^[1]
Wzb - a cytoplasmic regulatory phosphatase which dephosphorylates Wzc.^[1]
Wzc - a tyrosine kinase found in the bacterial inner membrane. Participates in polymerization of capsule polysaccharides.^[1]
Wzx - Transfers new polysaccharide units across the inner membrane.^[1]
Wzy - Assembles longer polysaccharide chains using units introduced by Wzx.^[1]

The CPS operon is likely transcriptionally regulated by the Rcs (regulation of capsule synthesis) proteins.^[1] Reduced levels of membrane-derived oligosaccharides result in autophosphorylation of RcsC. This results in a phosphate group being transferred from RcsC to RcsB. RcsB then binds to RcsA, forming a complex which acts on the CPS promoter and activates transcription of the CPS genes.

The same operon is present in Klebsiella species, possibly as a result of horizontal gene transfer.^[1]

References

^ ^a ^b ^c ^d ^e ^f ^g ^h Whitfield C (2006). "Biosynthesis and assembly of capsular polysaccharides in Escherichia coli". Annual Review of Biochemistry. 75: 39–68. doi:10.1146/annurev.biochem.75.103004.142545. PMID 16756484.