DNA affinity assay of the hupS / Npun_R0367 promoter region from Nostoc punctiforme ATCC 29133 and the hupS / asr0389 promoter region from Nostoc sp. strain PCC 7120 and total protein extract from respective strain. SDS-PAGE of proteins interacting with (A) the hupS/Npun_R0367 promoter region from N. punctiforme and (B) the hupS/asr0389 promoter region from Nostoc PCC 7120 from DNA-protein affinity assays. Lanes: M) protein molecular weight marker; 1) Total protein extract, 2) DNA-free negative control, 3) hupS/Npun_R0367 or hupS/asr0389 promoter region respectively. The unlabelled bands on the gel, present in both negative controls and samples, correspond to identified peptides either from unspecific binding, e.g. phycobilisome linker polypeptide (weak bands), artifacts from the experimental procedure, e.g. streptavidin (strongest band) or peptides with too low concentration to be identified (*).