SspA

SspA is an acronym used for several distinct proteins in different bacteria, and its precise meaning depends on the organism and context. The most common uses are described below.

In bacteria such as Escherichia coli and related species, SspA stands for string ent starvation protein A. This is a cytosolic protein associated with the bacterial stringent response to nutrient limitation. It is thought to influence transcription by interacting with RNA polymerase and is linked to the global shift in gene expression during stationary phase. Its activity is coordinated with other factors in the stringent response, and deletion of sspA can affect growth under stress and alter transcriptional programs.

In Bacillus and other spore-forming bacteria, SspA refers to a small acid-soluble spore protein (SASP). SASPs bind to DNA in dormant spores and help protect DNA from damage during long-term dormancy and environmental stresses. SspA (along with related SASPs such as SspB) plays a key role in maintaining spore viability and resistance properties during and after sporulation.

In some Streptococcus species, SspA denotes a Streptococcal surface protein A, an adhesin of the antigen I/II family. Surface-anchored SspA facilitates adherence to host surfaces, including the salivary pellicle and tooth surfaces, and often functions together with SspB as a tandem adhesin system. These proteins contribute to colonization and biofilm formation and can vary between species and strains.

Due to the shared acronym, SspA is best interpreted from organismal and functional context. See also SspB for related proteins in several systems.