SRP68

SRP68 is a 68-kilodalton protein subunit of the eukaryotic signal recognition particle (SRP). The SRP is a ribonucleoprotein complex that detects signal peptides on nascent polypeptides destined for secretion or membrane insertion and directs them to the endoplasmic reticulum (ER). In most eukaryotes, the SRP consists of the 7SL RNA and six protein subunits, including SRP68 and SRP72.

SRP68 is encoded by the SRP68 gene and forms a conserved heterodimer with SRP72 in the SRP S-domain. This heterodimer interacts with the SRP RNA and contributes to the structural organization of the complex, supporting binding to the signal sequence and positioning of the ribosome-nascent chain complex. SRP68 participates in the SRP's GTP-regulated cycle, aiding translation pause and targeting to the ER via the SRP receptor, in coordination with other SRP components such as SRP54.

Functionally, SRP68 operates in the cytosol during translation and is generally considered essential for cotranslational targeting of secretory and membrane proteins. The protein is evolutionarily conserved across eukaryotes and is widely expressed in human tissues.

Research on SRP68 has employed biochemical and structural approaches to characterize its interactions with SRP72, SRP RNA, and SRP54. While direct disease associations are not widely described, perturbations in SRP68 expression or function can disrupt protein targeting and secretion under stress or in certain genetic contexts.