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Title: THE MAIZE GENE HCF106 ENCODES AN ACIENT CONSERVED PROTEIN REQUIRED FOR SEC-INDEPENDENT PROTEIN TRANSLOCATION

Author
item SETTLES, MARK - COLD SPRING HARBOR LAB NY
item YONETAN, ANN - COLD SPRING HARBOR LAB NY
item BARON, AIMEE - COLD SPRING HARBOR LAB NY
item BUSH, DANIEL
item CLINE, KENNETH - UNIV FLORIDA GAINESVILLE
item MARTIENSSEN, ROB - COLD SPRING HAROBR LAB NY

Submitted to: Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/1/1997
Publication Date: N/A
Citation: N/A

Interpretive Summary: Plant leaves capture light energy from the sun and transforms it into a useful form in the process called photosynthesis. The unique compartment within the leaf cell that mediates this process is called the chloroplast. The chloroplast contains several specialized protein complexes that harvest the light energy. The constituent proteins of these complexes are imported from the cytoplasm of the cell by essential protein transport pathways. Mutations in these pathways disrupt photosynthesis and decrease crop yield. In spite of the significance of protein import, there is little known about the transport machinery inside the chloroplast. In the results reported here, a corn gene is described that encodes a protein that is part of a new, universal protein transport pathway that is found in both higher and lower organisms. This is an important contribution because it adds to our understanding of photosynthesis and because this protein is a potential target for herbicide development.

Technical Abstract: The bacterial Sec and SRP protein translocation mechanisms are conserved between prokaryotes and higher plant chloroplasts. However, there is a third translocation mechanism in chloroplasts that was previously thought to be unique. The hcf106 mutation of maize disrupts the localization of proteins transported through this pathway. We show here that this defect specifically blocks this pathway in isolated chloroplasts and that the HCF106 gene encodes a receptor-like thylakoid membrane protein. Significantly, the HCF106 protein shows homology to ORFs from all completely sequenced bacterial genomes, suggesting that sorting within the chloroplast has been conserved since the endosymbiotic event, and that HCF106 is a component of a third universal protein translocation pathway.