Histidine-Rich C-Terminal Tail of Mycobacterial GroEL1 and Its Copper Complex─The Impact of Point Mutations

The mycobacterial histidine-rich GroEL1 protein differs significantly compared to the well-known methionine/glycine-rich GroEL chaperonin. It was predicted that mycobacterial GroEL1 can play a significant role in the metal homeostasis of Mycobacteria but not, as its analogue, in protein folding. In this paper, we present the properties of the GroEL1 His-rich C-terminus as a ligand for Cu(II) ions. We studied the stoichiometry, stability, and spectroscopic features of copper complexes of the eight model peptides: L1-Ac-DHDHHHGHAH, L2- Ac-DKPAKAEDHDHHHGHAH, and six mutants of L2 in the pH range of 2-11. We revealed the impact of adjacent residues to the His-rich fragment on the complex stability: the presence of Lys and Asp residues significantly increases the stability of the system. The impact of His mutations was also examined: surprisingly, the exchange of each single His to the Gln residue did not disrupt the ability of the ligand to provide three binding sites for Cu(II) ions. Despite the most possible preference of the Cu(II) ion for the His9-His13 residues (Ac-DKPAKAEDHDHHH-) of the model peptide, especially the His11 residue, the study shows that there is not only one possible binding mode for Cu(II). The significance of this phenomenon is very important for the GroEL1 function -if the single mutation occurs naturally, the protein would be still able to interact with the metal ion

(2E)-2-Hydroxy­imino-N′-[(E)-2-pyridyl­methyl­ene]propanohydrazide

In the title compound, C9H10N4O2, the pyridine ring is twisted by 16.5 (1)° from the mean plane defined by the remaining non-H atoms. An intra­molecular N—H⋯N inter­action is present. In the crystal, inter­molecular O—H⋯N and N—H⋯O hydrogen bonds link mol­ecules into layers parallel to the bc plane. The crystal packing exhibits π–π inter­actions indicated by the short distance of 3.649 (1) Å between the centroids of the pyridine rings of neighbouring mol­ecules

Potassium 2-(N-hydroxy­carbamo­yl)acetate monohydrate

The crystal structure of the title compound, K+·C3H4NO4 −·H2O, consists of potassium cations, monoanions of 2-carboxy­acetohydroxamic acid [namely 2-(N-hydroxy­carbamo­yl)acetate] and solvent water mol­ecules. The elements of the structure are united in a three-dimensional network by numerous K⋯O coordinate bonds and O—H⋯O and N—H⋯O hydrogen bonds. The coordination sphere of the K+ ions may be described as a distorted double capped octa­hedron. Bond lengths and angles are similar to those in related compounds

Zn(II) and Cd(II) complexes of AMT1/MAC1 homologous Cys/His-Rich domains : so similar yet so different

Infections caused by Candida species are becoming seriously dangerous and difficult to cure due to their sophisticated mechanisms of resistance. The host organism defends itself from the invader, e.g., by increasing the concentration of metal ions. Therefore, there is a need to understand the overall mechanisms of metal homeostasis in Candida species. One of them is associated with AMT1, an important virulence factor derived from Candida glabrata, and another with MAC1, present in Candida albicans. Both of the proteins possess a homologous Cys/His-rich domain. In our studies, we have chosen two model peptides, L680 (Ac-10ACMECVRGHRSSSCKHHE27-NH2, MAC1, Candida albicans) and L681 (Ac-10ACDSCIKSHKAAQCEHNDR28-NH2, AMT1, Candida glabrata), to analyze and compare the properties of their complexes with Zn(II) and Cd(II). We studied the stoichiometry, thermodynamic stability, and spectroscopic parameters of the complexes in a wide pH range. When competing for the metal ion in the equimolar mixture of two ligands and Cd(II)/Zn(II), L680 forms more stable complexes with Cd(II) while L681 forms more stable complexes with Zn(II) in a wide pH range. Interestingly, a Glu residue was responsible for the additional stability of Cd(II)-L680. Despite a number of scientific reports suggesting Cd(II) as an efficient surrogate of Zn(II), we showed significant differences between the Zn(II) and Cd(II) complexes of the studied peptides

Dibromidobis(3,5-dimethyl-1H-pyrazole-κN 2)cobalt(II)

In the mononuclear title complex, [CoBr2(C5H8N2)2], the CoII atom is coordinated by two N atoms from two monodentate 3,5-dimethyl­pyrazole ligands and two Br atoms in a highly distorted tetra­hedral geometry. In the crystal, the complex mol­ecules are linked by inter­molecular N—H⋯Br hydrogen bonds into chains along [101]. An intra­molecular N—H⋯Br hydrogen bond is also present

Diaquabis­[3-(hydroxy­imino)­butanoato]nickel(II)

In the neutral, mononuclear title complex, [Ni(C4H6NO3)2(H2O)2], the Ni atom lies on a crystallographic inversion centre within a distorted octa­hedral N2O4 environment. Two trans-disposed anions of 3-hydroxy­imino­butanoic acid occupy four equatorial sites, coordinated by the deprotonated carboxyl­ate and protonated oxime groups and forming six-membered chelate rings, while the two axial positions are occupied by the water O atoms. The O atom of the oxime group forms an intra­molecular hydrogen bond with the coordinated carboxyl­ate O atom. The complex mol­ecules are linked into chains along b by hydrogen bonds between the water O atom and the carboxyl­ate O of a neighbouring mol­ecule. The chains are linked by further hydrogen bonds into a layer structure

Diaquabis­[3-(hydroxy­imino­)butanoato]nickel(II): a triclinic polymorph

The title centrosymmetric mononuclear complex, [Ni(C4H6NO3)2(H2O)2], is a polymorph of the previously reported complex [Dudarenko et al. (2010 ▶). Acta Cryst. E66, m277–m278]. The NiII atom, lying on an inversion center, is six-coordinated by two carboxyl­ate O atoms and two oxime N atoms from two trans-disposed chelating 3-hydroxy­imino­butanoate ligands and two axial water mol­ecules in a distorted octa­hedral geometry. The hydr­oxy group forms an intra­molecular hydrogen bond with the coordinated carboxyl­ate O atom. The complex mol­ecules are linked in stacks along [010] by a hydrogen bond between the water O atom and the carboxyl­ate O atom of a neighboring mol­ecule. The stacks are further linked by O—H⋯O hydrogen bonds into a layer parallel to (001)

cis-Bis(2,2′-bipyridine-κ2 N,N′)bis­(dimethyl sulfoxide-κO)zinc bis­(tetra­phenyl­borate) dimethyl sulfoxide monosolvate

In the mononuclear title complex, [Zn(C10H8N2)2(C2H6OS)2](C24H20B)2·C2H6OS, the ZnII ion is coordinated by four N atoms of two bidentate 2,2′-bipyridine mol­ecules and by the O atoms of two cis-disposed dimethyl sulfoxide mol­ecules in a distorted octa­hedral geometry. The S atom and the methyl groups of one of the coordinated dimethyl sulfoxide mol­ecules are disordered in a 0.509 (2):0.491 (2) ratio. The crystal packing is stabilized by C—H⋯O hydrogen bonds between the dimethyl sulfoxide solvent mol­ecules and tetra­phenyl­borate anions

Homeostasis of Zn(II) ions in infectious diseases

Zinc is an essential element for all living organisms, as it performs important functions in many biological processes; its presence was identified in over 300 enzymes. Due to the important functions it performs, living organisms have created mechanisms to maintain zinc ion homeostasis. In mammals, these mechanisms are also used to combat pathogens. Specialized immune cells are able to manipulate, in response to immune signals, intracellular and extracellular concentrations of zinc ions through metal-specific transporters and transfer proteins. These actions cause that the resulting environment becomes unfavourable for pathogens. The ability to rapidly regulate free zinc levels is critical to cytokine responses and the proliferation, and activation of cells belonging to the adaptive immune system