IMMUNOLOGICAL CHARACTERIZATION OF HYDROGENASES IN THE NITROGEN-FIXINGCYANOBACTERIUM NOSTOC SP STRAIN PCC-73102

N-2-fixing Nostoc sp. strain PCC 73102 was examined for the presence o f hydrogenases. Native-PAGE/immunoblots demonstrated that two proteins with molecular masses of approximately 200 kDa and 215 kDa are immuno logically related to hydrogenases purified from Bradyrhizobium japonic um, Azotobacter vinelandii, Methanosarcina barkeri, and Thiocapsa rose opersicina. SDS-PAGE/immunoblots showed that one polypeptide, with a m olecular mass of about 58 kDa, is immunologically related to the hydro genases purified from all the microorganisms mentioned above. In addit ion, two polypeptides, with molecular masses of approximately 34 and 7 0 kDa, are immunologically related to the hydrogenases purified from T . roseopersicina and M. barkeri respectively. Immunogold/transmission electron microscopy showed that the hydrogenase proteins are present i n both the heterocysts and the vegetative cells.