A Nitrite Excipient Database: A Useful Tool to Support N-Nitrosamine Risk Assessments for Drug Products.

N-Nitrosamine risk assessment and control have become an integral part of pharmaceutical drug product development and quality evaluation. Initial reports of nitrosamine contamination were linked with the drug substance and its manufacturing process. Subsequently, the drug product and aspects of the formulation process have shown to be relevant.

ICH Q3D Drug Product Elemental Risk Assessment: The Use of An Elemental Impurities Excipients Database.

The purpose of this publication is to show how an elemental impurities excipient database can be used in assisting the execution of a drug product elemental impurities risk assessment as required by the ICH Q3D guidelines. As a result of this exercise, we have demonstrated that the database, used in conjugation with other sources of information, is a credible source of elemental impurity levels in excipients therefore, a valuable source of information in completion of drug product risk assessments. This useful collection of data helps to reduce the burden of analytical testing for elemental impurities in excipients.

An Elemental Impurities Excipient Database: A Viable Tool for ICH Q3D Drug Product Risk Assessment.

To support the practical implementation of the International Council for Harmonisation (ICH) Q3D guideline, which describes a risk-based approach to the control of elemental impurities in drug products, a consortium of pharmaceutical companies has established a database to collate the results of analytical studies of the levels of elemental impurities within pharmaceutical excipients. This database currently includes the results of 26,723 elemental determinations for 201 excipients and represents the largest known, and still rapidly expanding, collection of data of this type. Analysis of the database indicates good coverage of excipients relevant to real-world drug product formulations and tested element profiles consistent with ICH Q3D recommendations.

The structural and energetic basis for high selectivity in a high-affinity protein-protein interaction.

High-affinity, high-selectivity protein-protein interactions that are critical for cell survival present an evolutionary paradox: How does selectivity evolve when acquired mutations risk a lethal loss of high-affinity binding? A detailed understanding of selectivity in such complexes requires structural information on weak, noncognate complexes which can be difficult to obtain due to their transient and dynamic nature. Using NMR-based docking as a guide, we deployed a disulfide-trapping strategy on a noncognate complex between the colicin E9 endonuclease (E9 DNase) and immunity protein 2 (Im2), which is seven orders of magnitude weaker binding than the cognate femtomolar E9 DNase-Im9 interaction. The 1.

Self-recognition by an intrinsically disordered protein.

The intrinsically disordered translocation domain (T-domain) of the protein antibiotic colicin N binds to periplasmic receptors of target Escherichia coli cells in order to penetrate their inner membranes. We report here that the specific 27 consecutive residues of the T-domain of colicin N known to bind to the helper protein TolA in target cells also interacts intramolecularly with folded regions of colicin N. We suggest that this specific self-recognition helps intrinsically disordered domains to bury their hydrophobic recognition motifs and protect them against degradation, showing that an impaired self-recognition leads to increased protease susceptibility.

Structure and Cu(I)-binding properties of the N-terminal soluble domains of Bacillus subtilis CopA.

CopA, a P-type ATPase from Bacillus subtilis, plays a major role in the resistance of the cell to copper by effecting the export of the metal across the cytoplasmic membrane. The N-terminus of the protein features two soluble domains (a and b), that each contain a Cu(I)-binding motif, MTCAAC. We have generated a stable form of the wild-type two-domain protein, CopAab, and determined its solution structure.

Flexibility in the receptor-binding domain of the enzymatic colicin E9 is required for toxicity against Escherichia coli cells.

The events that occur after the binding of the enzymatic E colicins to Escherichia coli BtuB receptors that lead to translocation of the cytotoxic domain into the periplasmic space and, ultimately, cell killing are poorly understood. It has been suggested that unfolding of the coiled-coil BtuB receptor binding domain of the E colicins may be an essential step that leads to the loss of immunity protein from the colicin and immunity protein complex and then triggers the events of translocation. We introduced pairs of cysteine mutations into the receptor binding domain of colicin E9 (ColE9) that resulted in the formation of a disulfide bond located near the middle or the top of the R domain.

Concerted folding and binding of a flexible colicin domain to its periplasmic receptor TolA.

Compared with folded structures, natively unfolded protein domains are over-represented in protein-protein and protein-DNA interactions. Such domains are common features of all colicins and are required for their translocation across the outer membrane of the target Escherichia coli cell. All of these domains bind to at least one periplasmic protein of the Tol or Ton family.

Structural dynamics of the receptor-binding domain of colicin E9.

Colicin E9 is a 61 kDa antibacterial protein secreted by E. coli. In order for it to enter the cytoplasm of susceptible bacteria and kill them by hydrolysing their DNA, the colicin must first interact with an outer membrane receptor on the target cell, BtuB, and a translocation pathway involving Tol proteins.

Structural dynamics of the membrane translocation domain of colicin E9 and its interaction with TolB.

In order for the 61 kDa colicin E9 protein toxin to enter the cytoplasm of susceptible cells and kill them by hydrolysing their DNA, the colicin must interact with the outer membrane BtuB receptor and Tol translocation pathway of target cells. The translocation function is located in the N-terminal domain of the colicin molecule. (1)H, (1)H-(1)H-(15)N and (1)H-(13)C-(15)N NMR studies of intact colicin E9, its DNase domain, minimal receptor-binding domain and two N-terminal constructs containing the translocation domain showed that the region of the translocation domain that governs the interaction of colicin E9 with TolB is largely unstructured and highly flexible.

PrrC from Rhodobacter sphaeroides, a homologue of eukaryotic Sco proteins, is a copper-binding protein and may have a thiol-disulfide oxidoreductase activity.

PrrC from Rhodobacter sphaeroides provides the signal input to a two-component signal transduction system that senses changes in oxygen tension and regulates expression of genes involved in photosynthesis (Eraso, J.M. and Kaplan, S.