Knowledge Bank

In this project, we investigated what determines whether a membrane protein inserts by the YidC/Sec-independent pathway, the YidC-only pathway, or the YidC/Sec pathway. Specifically, we wish to characterize the features of a membrane protein that determine path dependence. Our studies find that a membrane protein with a highly hydrophobic transmembrane segment inserts via the YidC/Sec-independent pathway. Addition of a negatively charged residue into the translocated periplasmic region or the transmembrane segment seems to switch insertion pathways to the YidC-only pathway, suggesting that charged residues in the translocated domain or transmembrane region is a YidC substrate determinant. On the other hand, the addition of a positively charged residue in the translocated domain or transmembrane of a membrane protein switches its insertion to the YidC/Sec pathway. We tested our studies initially using a single span membrane protein, and extended them to a protein that inserts with two hydrophobic domains. Our current findings indicate that that the YidC and YidC-Sec pathway have opposite charge requirements for membrane protein insertion.