Genomic arrangement of the ORFs upstream of the hyp -genes in Nostoc punctiforme ATCC 29133 and Nostoc sp. strain PCC 7120. (A) In the filamentous, heterocyst forming cyanobacterial strain N. punctiforme the five ORFs upstream of the hyp-genes are located upstream of the uptake hydrogenase structural genes, hupSL, and in between hupSL and the hyp-genes, hypFCDEAB. (B) The same genomic arrangement can be found in the filamentous, heterocyst forming cyanobacterial strain Nostoc PCC 7120. This genomic arrangement of the ORFs upstream of the hyp-genes seems to be conserved in filamentous cyanobacteria harboring an uptake hydrogenase  * indicates the 5' end of hupL (encoding the N-terminal end of HupL) as it is annotated in vegetative cells. The identified tsps upstream of hupSL , Npun_R0363  and Npun_R0367 (this work) in ATCC 29133 and upstream of asr0689, hypF and hypC in Nostoc PCC 7120  are indicated by arrows.