Cation Diffusion Facilitators Transport Initiation and Regulation Is Mediated by Cation Induced Conformational Changes of the Cytoplasmic Domain

Abstract

Cation diffusion facilitators (CDF) are part of a highly conserved protein family that maintains cellular divalent cation homeostasis in all domains of life. CDF's were shown to be involved in several human diseases, such as Type-II diabetes and neurodegenerative diseases. In this work, we employed a multi-disciplinary approach to study the activation mechanism of the CDF protein family. For this we used MamM, one of the main ion transporters of magnetosomes – bacterial organelles that enable magnetotactic bacteria to orientate along geomagnetic fields. Our results reveal that the cytosolic domain of MamM forms a stable dimer that undergoes distinct conformational changes upon divalent cation binding. MamM conformational change is associated with three metal binding sites that were identified and characterized. Altogether, our results provide a novel auto-regulation mode of action model in which the cytosolic domain's conformational changes upon ligand binding allows the priming of the CDF into its transport mode.

Functional Determinants of Metal Ion Transport and Selectivity in Paralogous Cation Diffusion Facilitator Transporters CzcD and MntE in Streptococcus pneumoniae

“…1) (24,27), relative to a splayed open, apo-state conformation observed in the isolated CTDs. The findings of previous studies of the CTD from Thermus thermophilus CzrB are consistent with those of the studies of the MamM CTD (28,29). Further in vivo characterization of MamM mutants harboring single or double alanine substitutions of putative C1/C2-site ligands found that the mutations disrupted metal transport activity and reduced magnetite crystal formation, suggesting that metal binding to the CTD facilitates metal transport (29).…”

“…The B site, in particular, has been proposed to stabilize the dimer to allow an alternating access (two-step) model of metal transport (27,28). A recent small-angle X-ray scattering and molecular dynamics analysis of the structurally characterized CTD of the magnetosome Fe transporter MamM of Magnetospirillum gryphiswaldense (29) suggests that Zn binding by the CTD induces a more tightly packed, closed, Vshaped structure like that found in the outward-facing conformation of the full-length E. coli YiiP (Fig. 1) (24,27), relative to a splayed open, apo-state conformation observed in the isolated CTDs.…”

REMOVAL OF CADMIUM AND LEAD BY ADAPTED STRAINS OF Pseudomonas aeruginosa AND Enterobacter cloacae

“…There are numerous additional examples such as the ability to withstand high arsenic concentrations described for several aquatic bacterial strains by Takeuchi et al (2007). This ability may be due to the activity of members of the cation diffusion facilitators (CDFs) family, which favors the efflux of divalent cations, thus preserving metal homeostasis (Zeytuni et al 2014), or to one or more of the several, sometimes overlapping, metal resistance systems summarized by Nies (2003) and more recently by Marrero-Coto et al (2010). …”

The unusual binding mechanism of Cu(ii) ions to the poly-histidyl domain of a peptide found in the venom of an African viper

“…We then coordinated Cu(II) with various residues along the sequence of the peptide using our previous protocol of constraints of metal binding with peptides and proteins. [34][35][36][37][38] We constructed models in which Cu(II) interacts with two or three imidazole groups of His and carboxylic groups of Glu or Asp and water, taking into account all the possibilities for the Cu(II)-pHpG-1 system. We selected ten models of the Cu(II)-pHpG-1 complex among the variety of the possible modes that Cu(II) can use to bind the peptide pHpG-1 (Table 4).…”