We will aim to determine the structures of two membrane transporters. (I) Na+-free form of the Na+-dependent dicarboxylate transporter VcINDY, a bacterial homolog of the human liver citrate transporter that is implicated in obesity. In the 2019 fall cycle, we collected images on VcINDY with Na+-bound, and were able to solve its structure at 3.1 Å resolution. Now we want to understand how Na+ gradient drives transport by solving the Na+-free structure of VcINDY. (II) Substrate-bound form of the antibiotic efflux pump NorA from Staphylococcus aureus, a drug transporter implicated in antibiotic resistance of MRSA. In the 2020 spring-summer cycle, we collected images at PNCC on two NorA-Fab complexes and obtained maps at 3.2 A and 3.7 A, respectively. We are currently in the process of tracing the chain in those maps. To understand the how NorA recognizes substrates, we aim to determine its structure in complex with various antibiotics.