Calcium Ions, Oxygen and Acetylene Reduction (Nitrogen Fixation) in the Unicellular Cyanobacterium Gloeocapsa sp. 1430/3

Synthesis and proteolytic degradation of nitrogenase in cultures of the unicellular cyanobacterium Gloeothece strain ATCC 27152

“…These included 1 pM PMSF or 4-(2-aminoethyl)-benzenesulphonyl fluoride (AEBSF), both inhibitors of serine proteases, and 1 mM Na,EDTA, which inhibits metalloproteases. In this last case, the inhibitor was added in the presence or absence of 5 mM CaCl,, which prevents the EDTA-mediated inhibition of nitrogenase activity in Gloeothece (Gallon & Harnadi, 1984;Hamadi & Gallon, 1981). Except when EDTA was added alone (in which case no activity was seen), these additions had little effect on nitrogenase activity, which had usually Completely disappeared by L1.…”

Calmodulin and calcium mediated regulation in prokaryotes

“…Calcium is known to be important in a mechanism which affords protection to the nitrogenase complex from O2 in both unicellular (Hamadi & Gallon, 1981 ;Gallon & Hamadi, 1984) and filamentous species (Rodriguez et al, 1990). Calmodulin inhibitors also inhibit nitrogenase activity in the presence of O2 and decrease the ability of an O2 stressed culture to recover N2 fixation (Onek,199 1).…”

THE EFFECT OF ABSCISIC ACID ON CALCIUM‐MEDIATED REGULATION OF HETEROCYST FREQUENCY AND NITROGENASE ACTIVITY IN NOSTOC 6720

“…A Ca^"'"-dependent mechanism which protects the nitrogenase activity of Gleocapsa sp. from oxygen has been proposed (Falah Hamadi & Gallon, 1981;Gallon & Falah Hamadi, 1984). The enhancement might therefore be explained in terms of the elevated intracellular concentration of Ca^"*" which is common to both treatments (Table 2; Smith et al, 1987).…”