A notable example is the streptococcal hemoprotein receptor (Shr), a surface protein with a role in iron uptake that has no significant homologues in other bacteria but shares partial homology with eukaryotic receptors such as Toll and G-protein dependent receptors (gi 15675635, GenBank). Additional sequence analysis identified a leucine-rich repeat domain, an EF-hand Ca 2+ domain, and two NEAT domains [50] . As shown in Figure 4 , the single EF-hand motif identified in Shr has a significant homology to that of CaM with all the conserved Ca 2+ binding ligand residues and two flanking helices (Figure 4 ).