Four rhoptry proteins (ROP) of Toxoplasma gondii previously identified with mAb have been affinity purified and analyzed by MS; the data obtained allowed the genomic sequences to be assigned to these proteins. As previously suggested for some of them by antibody crossreactivity, these proteins were shown to belong to a family, the prototype of which being ROP2. We describe here the proteins ROP2, 4, 5, and 7. These four proteins correspond to the most abundant products of a gene family that comprises several members which we have identified in genomic and EST libraries. Eight additional sequences were found and we have cloned four of them. All members of the ROP2 family contain a protein-kinase-like domain, but only some of them possess a bona fide kinase catalytic site. Molecular modeling of the kinase domain demonstrates the conservation of residues critical for the stabilization of the protein-kinase fold, especially within a hydrophobic segment described so far as transmembrane and which appears as an helix buried inside the protein. The concomitant synthesis of these ROPs by T. gondii tachyzoites suggests a specific role for each of these proteins, especially in the early interaction with the host cell upon invasion.

Aerobic respiration metabolism in Group B Streptococcus (GBS) is activated by exogenous heme and menaquinone. This capacity enhances resistance of GBS to acid and oxidative stress and improves its survival. In this work, we discovered that GBS is able to respire in the presence of heme and 1,4-dihydroxy-2-naphthoic acid (DHNA). DHNA is a biosynthetic precursor of demethylmenaquinone (DMK) in many bacterial species. A GBS gene (gbs1789) encodes a homolog of the MenA 1,4-dihydroxy-2-naphthoate prenyltransferase enzyme, involved in the synthesis of demethylmenaquinone. In this study, we showed that gbs1789 is involved in the biosynthesis of long-chain demethylmenaquinones (DMK-10). The Δgbs1789 mutant cannot respire in the presence of heme and DHNA, indicating that endogenously synthesized DMKs are cofactors of the GBS respiratory chain. We also found that isoprenoid side chains from GBS DMKs are produced by the protein encoded by the gbs1783 gene, since this gene can complement an Escherichia coli ispB mutant defective for isoprenoids chain synthesis. In the gut or vaginal microbiote, where interspecies metabolite exchanges occur, this partial DMK biosynthetic pathway can be important for GBS respiration and survival in different niches.