The MicA RNA is a small non-coding RNA

Non-coding RNA

A non-coding RNA is a functional RNA molecule that is not translated into a protein. Less-frequently used synonyms are non-protein-coding RNA , non-messenger RNA and functional RNA . The term small RNA is often used for short bacterial ncRNAs...

 that was discovered in E. coli during a large scale screen. Expression of SraD is highly abundant in stationary phase, but low levels could be detected in exponentially growing

Bacterial growth

250px|right|thumb|Growth is shown as L = log where numbers is the number of colony forming units per ml, versus T Bacterial growth is the division of one bacterium into two daughter cells in a process called binary fission. Providing no mutational event occurs the resulting daughter cells are...

 cells as well.

Function

This RNA binds the Hfq protein

Hfq protein

The Hfq protein encoded by the hfq gene was discovered in 1968 as an Escherichia. coli host factor that was essential for replication of the bacteriophage Qβ. It is now clear that Hfq is an abundant bacterial RNA binding protein which has many important physiological roles. Usually mediated by...

 and regulates levels of gene expression

Gene expression

Gene expression is the process by which information from a gene is used in the synthesis of a functional gene product. These products are often proteins, but in non-protein coding genes such as ribosomal RNA , transfer RNA or small nuclear RNA genes, the product is a functional RNA...

 by an antisense mechanism. It is known to target the OmpA gene in E. coli and occludes the ribosome binding site. Under conditions of envelope stress, micA transcription is induced. MicA and RybB RNA

RybB RNA

RybB is a small non-coding RNA was identified in a large scale screen of E. coli. The function of this short RNA has been studied using a transcriptomic approach and kinetic analyses of target mRNA decay in vivo. RybB was identified as a factor that selectively accelerates the decay of multiple...

 transcription is under the control of the sigma factor

Sigma factor

A sigma factor is a bacterial transcription initiation factor that enables specific binding of RNA polymerase to gene promoters. Different sigma factors are activated in response to different environmental conditions...

 sigma(E).

The PhoPQ two-component system is repressed by MicA.
The RNA presumably pairs with the ribosomal binding site

Ribosomal Binding Site

A ribosomal binding site is a sequence on mRNA that is bound by the ribosome when initiating protein translation.It can be either the 5' cap of a messenger RNA in eukaryotes, a region 6-7 nucleotides upstream of the start codon AUG in prokaryotes , or an internal ribosome entry site in viruses...

 of phoP mRNA, thereby inhibiting translation.
This links micA to cellular processes such as Mg(2+) transport, virulence

Virulence

Virulence is by MeSH definition the degree of pathogenicity within a group or species of parasites as indicated by case fatality rates and/or the ability of the organism to invade the tissues of the host. The pathogenicity of an organism - its ability to cause disease - is determined by its...

, LPS modifications and resistance to antimicrobial peptides.

In S. typhimurium MicA has been shown to be involved in biofilm

Biofilm

A biofilm is an aggregate of microorganisms in which cells adhere to each other on a surface. These adherent cells are frequently embedded within a self-produced matrix of extracellular polymeric substance...

formation.