Roles of Type VI Secretion System in Transport of Metal Ions

The type VI secretion system (T6SS) is a transmembrane protein nanomachine employed by many gram-negative bacteria to directly translocate effectors into adjacent cells or the extracellular milieu, showing multiple functions in both interbacterial competition and bacteria-host interactions. Metal ion transport is a newly discovered T6SS function. This review summarizes the identified T6SS functions and highlights the features of metal ion transport mediated by T6SS and discusses its regulation.

Mitochondrial Metal Ion Transport in Cell Metabolism and Disease

Mitochondria are vital to life and provide biological energy for other organelles and cell physiological processes. On the mitochondrial double layer membrane, there are a variety of channels and transporters to transport different metal ions, such as Ca2+, K+, Na+, Mg2+, Zn2+ and Fe2+/Fe3+. Emerging evidence in recent years has shown that the metal ion transport is essential for mitochondrial function and cellular metabolism, including oxidative phosphorylation (OXPHOS), ATP production, mitochondrial integrity, mitochondrial volume, enzyme activity, signal transduction, proliferation and apoptosis. The homeostasis of mitochondrial metal ions plays an important role in maintaining mitochondria and cell functions and regulating multiple diseases. In particular, channels and transporters for transporting mitochondrial metal ions are very critical, which can be used as potential targets to treat neurodegeneration, cardiovascular diseases, cancer, diabetes and other metabolic diseases. This review summarizes the current research on several types of mitochondrial metal ion channels/transporters and their functions in cell metabolism and diseases, providing strong evidence and therapeutic strategies for further insights into related diseases.

New Polymer Inclusion Membranes in the Separation of Palladium, Zinc and Nickel Ions from Aqueous Solutions

The new polymer inclusion membrane (PIM) with a 1-alkyltriazole matrix was used to separate palladium(II) ions from aqueous chloride solutions containing a mixture of Zn-Pd-Ni ions. The effective conditions for transport studies by PIMs were determined based on solvent extraction (SX) studies. Furthermore, the values of the stability constants and partition coefficients of M(II)-alkyltriazole complexes were determined. The values of both constants increase with the growing hydrophobicity of the 1-alkyltriazole molecule and have the highest values for the Pd(II) complexes. The initial fluxes, selectivity coefficients, and recovery factors values of for Pd, Zn and Ni were determined on the basis of membrane transport studies. The transport selectivity of PIMs were: Pd(II) > Zn(II) > Ni(II). The initial metal ion fluxes for all the cations increased with the elongation of the alkyl chain in the 1-alkyltriazole, but the selectivity coefficients decreased. The highest values of the initial fluxes at pH = 4.0 were found for Pd(II) ions. The best selectivity coefficients Pd(II)/Zn(II) and Pd(II)/Ni(II) equal to 4.0 and 13.4, respectively, were found for 1-pentyl-triazole. It was shown that the microstructure of the polymer membrane surface influences the kinetics of metal ion transport. Based on the conducted research, it was shown that the new PIMs with 1-alkyltriazole can be successfully used in an acidic medium to separate a mixture containing Pd(II), Zn(II) and Ni(II) ions.

Some aspects of metal ion transport and in silico gene expression analysis of potassium/sodium ion transporters, channels and exchangers in root nodules

Rhizobia establish a symbiotic relationship with legumes, which results in the formation of root nodules, the ecological niche for intracellular rhizobia. The infected cell of a root nodule is a special integral unit of plant and nitrogen fixing rhizobia. Nodules tend to be very sensitive to ionic stresses, such as salt stress. High vulnerability toward ionic stresses might be due to defects in ion balance and transport in the infected tissue. The purpose of this minireview is to summarize the current data regarding metal ion transport in the root nodule, with particular emphasis on potassium/sodium ion transport. A bioinformatic approach and in silico gene expression analysis have been used to obtain some insight for K+/Na+ transportеr channels and exchangers in root nodule developmental zones.

Synthetic Bio-Inorganic Materials in Various Artificial Organs

Bioinorganic materials play the important role in all living organisms. Mostly these compounds are responsible for the vital actions of an organism such as enzymatic actions, respiration, photosynthesis, metal ion transport etc. In recent time numerous bioinorganic materials have been synthesized partially or completely in the laboratories. These synthetic bioinorganic materials serve as medical boon for mankind as they are the key for development of artificial tissues and organs. In this paper we are discussing about artificial organs and related bioinorganic materials.

Mechanistic basis of the inhibition of SLC11/NRAMP-mediated metal ion transport by bis-isothiourea substituted compounds

In humans, the divalent metal ion transporter-1 (DMT1) mediates the transport of ferrous iron across the apical membrane of enterocytes. Hence, its inhibition could be beneficial for the treatment of iron overload disorders. Here we characterize the interaction of aromatic bis-isothiourea-substituted compounds with human DMT1 and its prokaryotic homologue EcoDMT. Both transporters are inhibited by a common competitive mechanism with potencies in the low micromolar range. The crystal structure of EcoDMT in complex with a brominated derivative defines the binding of the inhibitor to an extracellular pocket of the transporter in direct contact with residues of the metal ion coordination site, thereby interfering with substrate loading and locking the transporter in its outward-facing state. Mutagenesis and structure-activity relationships further support the observed interaction mode and reveal species-dependent differences between pro- and eukaryotic transporters. Together, our data provide the first detailed mechanistic insight into the pharmacology of SLC11/NRAMP transporters.