Studies on outer membrane stability and permeability of primitive chloroplasts and its evolutionary relationships between Gram-negative bacteria

2016 Fiscal Year Final Research Report

• Project/Area Number: 15K20860
• Research Category: Grant-in-Aid for Young Scientists (B)
• Allocation Type: Multi-year Fund
• Research Field: Evolutionary biology; Morphology/Structure
• Research Institution: Tohoku University
• Principal Investigator: KOJIMA Seiji 東北大学, 学際科学フロンティア研究所, 助教 (20745111)
• Project Period (FY): 2015-04-01 – 2017-03-31
• Keywords: 細胞壁ペプチドグリカン / チャネル / 外膜 / グラム陰性細菌 / 葉緑体 / 灰色藻 / 藍藻

Outline of Final Research Achievements

During the course of evolution from an endosymbiotic cyanobacterium to the chloroplast, the function of the outer membrane changed from permeability barrier to an interface that connects two metabolic entities, the chloroplast and host cell. In order to know how this functional alteration was possible, I studied on the outer membrane of primitive chloroplast (chloroplast of Cyanophora paradoxa).
I discovered two dominant proteins from the outer membrane of C. paradoxa chloroplast, and named them CppS and CppF. They function as non-specific diffusion channel. Surprisingly, their amino acid sequences showed no evolutionary linkage to cyanobacteria. My findings suggest that C. paradoxa chloroplast adopted the non-cyanobacterial proteins as its main outer membrane components, providing a diffusion route for various small substances across the outer membrane.

Free Research Field

細菌および葉緑体の膜生化学