PubMed:10545095 JSONTXT

{"project":"PMID_GLOBAL","denotations":[{"id":"T1","span":{"begin":0,"end":150},"obj":"Sentence"},{"id":"T2","span":{"begin":151,"end":293},"obj":"Sentence"},{"id":"T3","span":{"begin":294,"end":398},"obj":"Sentence"},{"id":"T4","span":{"begin":399,"end":525},"obj":"Sentence"},{"id":"T5","span":{"begin":526,"end":606},"obj":"Sentence"},{"id":"T6","span":{"begin":607,"end":783},"obj":"Sentence"},{"id":"T7","span":{"begin":784,"end":962},"obj":"Sentence"},{"id":"T8","span":{"begin":963,"end":1133},"obj":"Sentence"},{"id":"T9","span":{"begin":1134,"end":1276},"obj":"Sentence"},{"id":"T10","span":{"begin":1277,"end":1336},"obj":"Sentence"}],"text":"Targeted inactivation of the smallest plastid genome-encoded open reading frame reveals a novel and essential subunit of the cytochrome b(6)f complex.\nThe smallest conserved open reading frame in the plastid genome, ycf6, potentially specifies a hydrophobic polypeptide of only 29 amino acids. In order to determine the function of this reading frame we have constructed a knockout allele for ycf6. This allele was introduced into the tobacco plastid genome by chloroplast transformation to replace the wild-type ycf6 allele. Homoplasmic Deltaycf6 plants display a photosynthetically incompetent phenotype. Whereas the two photosystems are intact and physiologically active, we found that the electron transfer from photosystem II to photosystem I is interrupted in Deltaycf6 plants. Molecular analyses revealed that this block is caused by the complete absence of the cytochrome b(6)f complex, the redox-coupling complex that interconnects the two photosystems. Analysis of purified cytochrome b(6)f complex by mass spectroscopy revealed the presence of a protein that has exactly the molecular mass calculated for the Ycf6 protein. This suggests that Ycf6 is a genuine subunit of the cytochrome b(6)f complex, which plays a crucial role in complex assembly and/or stability. We therefore propose to rename the ycf6 reading frame petN."}