Recently, the reporter learned from West Lake University that the research of Yan Zhen, a distinguished researcher in the School of Life Sciences of the University, has revealed the mystery of chloroplast protein transport, and its research results were published online in the journal Cell. "Photosynthesis is known as the most important chemical reaction on the earth." Yan Zhen introduced that chloroplast, as an important site for photosynthesis, is like a "light factory". There are 2000 to 3000 kinds of proteins that need to be identified by TOC-TIC complex and then enter the chloroplast to "work". Previously, the scientific community has found that chloroplast is a double membrane structure. There is a transport factor TIC on the inner membrane and a transport factor TOC on the outer membrane. They combine to form a super complex TOC-TIC and act as the "gatekeeper" of chloroplast. Yan Zhen Laboratory hopes to further reveal the composition, assembly and transport mechanism of TOC-TIC complex by means of biochemistry and structural biology. They selected the TOC-TIC super complex of Chlamydomonas kleinii as the research object, and added affinity labels on two TOC (Toc34) and TIC (Tic20) components that have been identified and highly conserved in different species for purification. "That is to set up two groups of experiments. In specific chloroplast samples, the TOC-TIC complex was accurately found and purified through affinity tags." Yan Zhen explained that, thankfully, the protein components purified by these two different strategies were completely identical, and the electron microscope structures analyzed were also highly consistent. The analysis results showed that the TOC-TIC super complex on the chloroplast of Chlamydomonas kleinii contained 14 components, including 8 previously reported components and 6 new components with unknown functions. Based on previous theories, it is believed that on the bilayer chloroplast membrane, the protein carries the transport signal peptide to enter the chloroplast successively through the important channel of TOC-TIC super complex. (Liu Xinshe)