One of the most fundamental processes within the cell is ensuring that translated proteins are compartmentalised to their appropriate location to ensure cell survival. To ensure that this process occurs correctly and efficiently, the cell employs several pathways to transport each protein to their designated area. There are two main transport systems for protein transport, which occur during (co-translational) or after (post-translational) the process of translation. These protein transport systems are highly characterised; however the protein complexes that mediate these pathways are not well understood. We are interested in the human ribonucleoprotein complex involved in the process of co-translational translocation known as the signal recognition particle (SRP), which is known to transport nascent proteins destined for the endoplasmic reticulum (ER) from the cytosol. To perform this function, the SRP has two functional domains known as the Alu and S domain, which are necessary for elongation arrest (Alu domain), recognition of the signal sequence and ER targeting (S domain).
In this complex we want to specifically understand the functions of the heterodimer, the signal recognition particle protein-68/72 (SRP68/72), which are two of the four proteins that comprise the S domain along with 7S RNA. Our aim is to understand its role in the complex during the process of co-translational translocation by characterising its function on 7S RNA. Through this, we would like to gain a better understanding of how it binds to 7S RNA alone and in conjunction with other SRP proteins using electrophoretic mobility shift assays (EMSA) and microscale thermophoresis (MST). Currently we have shown through these techniques, the protein-RNA interactions between the RNA-binding domains of SRP68 and SRP72 to 7S RNA. Furthermore using NMR data obtained in the lab and past literature, point mutations on the SRP72 RBD and 7S RNA have been tested to elucidate the RNA-protein interactions.