Signal Recognition Particle (SRP) 抑制因子

The Signal Recognition Particle (SRP) ribonucleoprotein (protein-RNA complex) is a fundamental cellular machinery essential for the co-translational targeting of proteins to specific cellular membranes, such as the endoplasmic reticulum (ER) in eukaryotic cells or the inner membrane in prokaryotic cells. This complex plays a critical role in ensuring that newly synthesized proteins are accurately directed to their appropriate destinations within the cell. The SRP complex consists of two primary components: a small cytoplasmic RNA molecule known as 7S RNA (in eukaryotes) or 4.5S RNA (in bacteria) and a protein component known as SRP protein or Ffh (Fifty-four homolog).

The primary function of the SRP ribonucleoprotein complex is to recognize, bind to, and target signal peptide sequences found at the N-terminus of nascent polypeptide chains as they emerge from ribosomes during translation. The SRP identifies these signal peptides as they emerge from the ribosome's exit tunnel, forming a ribosome-SRP complex. This binding event temporarily halts protein synthesis. Subsequently, the SRP guides the ribosome-nascent chain complex to the ER membrane in eukaryotes or the plasma membrane in prokaryotes. This process is orchestrated through interactions with the SRP receptor (SR) on the membrane, leading to the transfer of the nascent polypeptide to the translocon, a protein-conducting channel, for further translocation across or insertion into the membrane. SRP inhibitors are designed to interfere with the recognition and binding of signal peptides by the SRP, the interaction between the SRP and ribosomes, or the interaction between the SRP and its receptor on the target membrane.