Feo--transport of ferrous iron into bacteria.

Bacteria commonly utilise a unique type of transporter, called Feo, to specifically acquire the ferrous (Fe2+) form of iron from their environment. Enterobacterial Feo systems are composed of three proteins: FeoA, a small, soluble SH3-domain protein probably located in the cytosol; FeoB, a large protein with a cytosolic N-terminal G-protein domain and a C-terminal integral inner-membrane domain containing two 'Gate' motifs which likely functions as the Fe2+ permease; and FeoC, a small protein apparently functioning as an [Fe-S]-dependent transcriptional repressor. We provide a review of the current literature combined with a bioinformatic assessment of bacterial Feo systems showing how they exhibit common features, as well as differences in organisation and composition which probably reflect variations in mechanisms employed and function.

Phylogenetic and evolutionary analysis of the PLUNC gene family.

The PLUNC family of human proteins are candidate host defense proteins expressed in the upper airways. The family subdivides into short (SPLUNC) and long (LPLUNC) proteins, which contain domains predicted to be structurally similar to one or both of the domains of bactericidal/permeability-increasing protein (BPI), respectively. In this article we use analysis of the human, mouse, and rat genomes and other sequence data to examine the relationships between the PLUNC family proteins from humans and other species, and between these proteins and members of the BPI family. We show that PLUNC family clusters exist in the mouse and rat, with the most significant diversification in the locus occurring for the short PLUNC family proteins. Clear orthologous relationships are established for the majority of the proteins, and ambiguities are identified. Completion of the prediction of the LPLUNC4 proteins reveals that these proteins contain approximately a 150-residue insertion encoded by an additional exon. This insertion, which is predicted to be largely unstructured, replaces the structure homologous to the 40s hairpin of BPI. We show that the exon encoding this region is anomalously variable in size across the LPLUNC proteins, suggesting that this region is key to functional specificity. We further show that the mouse and human PLUNC family orthologs are evolving rapidly, which supports the hypothesis that these proteins are involved in host defense. Intriguingly, this rapid evolution between the human and mouse sequences is replaced by intense purifying selection in a large portion of the N-terminal domain of LPLUNC4. Our data provide a basis for future functional studies of this novel protein family.