To obtain the subject new compound useful for screening of antibacterial compounds and for e.g. treatment and diagnosis of infectious diseases and comprising a ftsZ polypeptide having various degrees of the sameness as a specific amino acid sequence over its full length.

This new ftsZ polypeptide comprises e.g. an isolated polypeptide comprising an amino acid sequence having at least 70%, or 80%, 90% or 95% of the isentity as each amino acid sequence of formula I or II over its full length, or an isolated polypeptide being an amino acid sequence of formula I or II or comprising such a amino acid sequence. The obtained polypeptide is useful for screening of antibacterial compounds and for e.g. treatment and diagnosis of Streptococcus pneumoniae infection. The polypeptide is obtained by probing a chromosome DNA library of Streptococcus pneumoniae by a partial sequence-derived labeled oligonucleotide and integrating the obtained polynucleotide into an expression system for its expression.