Biogenesis of chlorophyll binding electron transfer complexes

Hvordan er bindingen av klorofyll til proteiner fra fotosyntetiske komplekser regulert i planter? Fotosystemer inneholder klorofyllbindende proteinkomplekser for fysisk og kjemisk transformasjon av lysenergi til en kjemisk lagringsform. Hvordan klorofyllmolekylene er samlet i det fotosyntetiske maskineriet, som fungerer som primære steder for begge prosesser, er ukjent. Vi har etablert en in vitro-modell for å studere bindingen av klorofyll til proteinkomplekser og spesielt til fotosystemkomplekser. I prosjektet har vi karakterisert et bindingssete for klorofyll a i LIL3, der klorofyll binder umiddelbart etter syntese. En modell for overføring av klorofyll dette fotosystemkomplekset er blitt etablert og er nå verifisert eksperimentelt.

The project has opened new possibilities for the work career of two postdoctoral scientists in the field of protein biochemistry. The technologies developed in the project are now applied for investigations in the area of medicine and industry. The postdocs have in part reached a developmental status to now apply for Professorship positions. The institute profits from the extended collaborative network established by the researchers. The local industry profits from the knowledge gain to extend and shape new products.

Since more than 10E9 years, nature operates endosymbiotic metabolic pathways in eukaryotic host cells. In plants, maintenance of the cells metabolism is compartmentalized. The metabolic stage of a family of plastid organelles defines the metabolic developmental stage of the plant. The chlorophyll binding electron transport protein complexes in the endosymbiontic chloroplast are the cornerstone in the evolutionary invention of nature to maintain a photoautotrophic metabolism and are the central regulatory process for survival of the plant. However, very little is known about the coordinated biogenesis of chlorophyll and of the chlorophyll binding proteins and their assembly. We established an experimental system using etioplasts from barley and mutants from Arabidopsis that provide excellent biochemical and genetic systems to characterize the complex biogenetic processes. Upon illumination, the switch in the developmental program can be studied in vivo and in vitro top down down to the molecular level. A novel method developed throughout the last two years has demonstrated that a fast and high-resolution isolation of native assemblies of multienzyme complexes is now possible. The method is key to isolate the hypercomplex assemblies for chlorophyll and protein synthesis, assembly of the chlorophyll binding proteins of the electron transfer chain and for the study of their coordinated action. We will focus on the isolation and characterization of the enzymatic activity of the assemblies in developmental and mutant studies using plants, bacteria and algae. Structural and special functional characterizations of the recently identified complexes for Chl and electron transfer will be conducted by single particle electron tomography and femtosecond crystallography in collaboration with our partners on site. The laboratory has developed an exciting degree of compentence for resolving this most extraordinary and essential regulatory biochemical pathway.