A 4.5-kb BamHI fragment of chromosomal DNA of Streptomyces collinus containing gene ftsZ was cloned and sequenced. Upstream of ftsZ are localized genes ftsQ, murG, and ftsW, and downstream is yfiH. Gene ftsA is not adjacent to ftsZ or other genes of the cloned fragment. Protein FtsZ was isolated and characterized with respect to its binding to GTP and GTPase activity. The binding of GTP to FtsZ was Ca2+ or Mg2+ dependent with an optimum at 10 mM. The rate of GTP hydrolysis by FtsZ was stimulated by KCl. The presence of Ca2+ (3-5 mM) resulted in a significant increase of GTPase activity. Higher concentrations of Ca2+ than 5 mM, had an inhibitory effect on GTPase activity. These results indicate that divalent ions (Ca2+ or Mg2+) can be involved in regulation of GTP binding and hydrolysis of FtsZ, The maximum level of FtsZ was detected in aerial mycelium when spiral loops and sporulation septa were formed. FtsZ is degraded after finishing sporulation septa.