PubMed:10217509 JSONTXT

{"project":"CyanoBase","denotations":[{"id":"T1","span":{"begin":490,"end":494},"obj":"protein"},{"id":"T2","span":{"begin":495,"end":499},"obj":"protein"},{"id":"T3","span":{"begin":500,"end":504},"obj":"protein"},{"id":"T4","span":{"begin":536,"end":540},"obj":"protein"},{"id":"T5","span":{"begin":542,"end":546},"obj":"protein"},{"id":"T6","span":{"begin":548,"end":552},"obj":"protein"},{"id":"T7","span":{"begin":554,"end":558},"obj":"protein"},{"id":"T8","span":{"begin":563,"end":567},"obj":"protein"},{"id":"T9","span":{"begin":622,"end":626},"obj":"protein"},{"id":"T10","span":{"begin":627,"end":631},"obj":"protein"},{"id":"T11","span":{"begin":632,"end":636},"obj":"protein"},{"id":"T12","span":{"begin":637,"end":641},"obj":"protein"},{"id":"T13","span":{"begin":673,"end":677},"obj":"protein"},{"id":"T14","span":{"begin":729,"end":733},"obj":"protein"},{"id":"T15","span":{"begin":735,"end":739},"obj":"protein"},{"id":"T16","span":{"begin":741,"end":745},"obj":"protein"},{"id":"T17","span":{"begin":747,"end":751},"obj":"protein"},{"id":"T18","span":{"begin":753,"end":757},"obj":"protein"},{"id":"T19","span":{"begin":843,"end":847},"obj":"protein"},{"id":"T20","span":{"begin":883,"end":887},"obj":"protein"},{"id":"T21","span":{"begin":901,"end":905},"obj":"protein"},{"id":"T22","span":{"begin":906,"end":910},"obj":"protein"},{"id":"T23","span":{"begin":911,"end":915},"obj":"protein"},{"id":"T24","span":{"begin":920,"end":924},"obj":"protein"},{"id":"T25","span":{"begin":1015,"end":1019},"obj":"protein"},{"id":"T26","span":{"begin":1024,"end":1028},"obj":"protein"},{"id":"T27","span":{"begin":1288,"end":1292},"obj":"protein"},{"id":"T28","span":{"begin":1293,"end":1297},"obj":"protein"},{"id":"T29","span":{"begin":1299,"end":1303},"obj":"protein"},{"id":"T30","span":{"begin":1309,"end":1313},"obj":"protein"}],"text":"Organization and expression of nitrogen-fixation genes in the aerobic nitrogen-fixing unicellular cyanobacterium Synechococcus sp. strain RF-1.\nSixteen nif and 'nif-associated' genes (expressed only under conditions of nitrogen fixation) in Synechococcus sp. strain RF-1 have been cloned and sequenced. All of the nif and nif-associated genes identified in Synechococcus RF-1 were arranged in a continuous cluster spanning approximately 18 kb and containing seven operons. The nifH operon (nifH-nifD-nifK) has been reported previously. nifB, fdxN, nifS, nifU and nifP were found to be located upstream of the nifH operon. nifB-fdxN-nifS-nifU were expressed as an operon. A nifP-like gene was found to be located just upstream of nifB. nifE, nifN, nifX, nifW and the nif-associated hesA, hesB and 'fdx' were found to be located downstream from nifK. The genes located downstream from nifK are arranged nifE-nifN-nifX-orf-nifW-hesA-hesB-'+ ++fdx' and span approximately 7 kb. The function of the ORF situated between nifX and nifW is not known. However, it was identified as a counterpart of ORF-2 in Anabaena sp. strain PCC 7120 based on the deduced amino acid sequence. Northern hybridization and primer extension analysis indicated that the nif and nif-associated genes are organized in nifE-nifN, nifX-orf, nifW-hesA-hesB and 'fdx'-containing operons, respectively. According to the results of this study and previous reports, the genes are expressed in a rhythmic pattern with peaks during the dark phase when the culture is grown in a 12 h light/12 h dark regimen. The rhythm persisted after the culture was transferred to continuous illumination."}