Primary structure-based function characterization of BRCT domain replicates in BRCA1

Dual Modulators of p53 and Cyclin D in ER Alpha Signaling by Albumin Nanovectors Bearing Zinc Chaperones for ER-positive Breast Cancer Therapy

CDATA[The inherited mutations and underexpression of BRCA1 in sporadic breast cancers resulting in the loss or functional inactivation of BRCA1 may contribute to a high risk of breast cancer. Recent researchers have identified small molecules (BRCA1 mimetics) that fit into a BRCA1 binding pocket within Estrogen Receptor alpha (ERα), mimic the ability of BRCA1 to inhibit ERα activity, and overcome antiestrogen resistance. Studies indicate that most of the BRCA1 breast cancer cases are associated with p53 mutations. It indicates that there is a potential connection between BRCA1 and p53. Most p53 mutations are missense point mutations that occur in the DNA-binding domain. Structural studies have demonstrated that mutant p53 core domain misfolding, especially p53-R175H, is reversible. Mutant p53 reactivation with a new class of zinc metallochaperones (ZMC) restores WT p53 structure and functions by restoring Zn²⁺ to Zn²⁺ deficient mutant p53. Considering the role of WT BRCA1 and reactivation of p53 in tumor cells, our hypothesis is to target both tumor suppressor proteins by a novel biomolecule (ZMC). Since both proteins are present in the same cell and are functionally inactive, this state may be a novel efficacious therapeutic regime for breast cancer therapy. In addition, we propose to use Albumin Nanovector (ANV) formulation for target drug release.

Homology versus analogy: possible evolutionary relationship of immunoglobulins, cupredoxins, and Cu,Zn-superoxide dismutase

The 'immunoglobulin-like' fold is one of most common structural motifs observed in proteins. This topology is found in more than 80 superfamilies of proteins, including Cu,Zn-superoxide dismutase (SOD) and cupredoxin. Evolutionary relationships have not been identified, but may exist. The challenge remains, therefore, of resolving the issue of whether the diverse distribution of the fold is accounted for by divergent evolution of function or convergent evolution of structure following multiple independent origins of function. Since the early studies that revealed conformational similarity of immunoglobulins and other proteins, the number of primary structures available for comparison has dramatically increased and new computational approaches for analysis of sequences have been developed. It now appears that a hypothesis of a common evolutionary origin for cupredoxins, Cu,Zn-SOD, and immunoglobulins may be credible. The distinction between protein homology and protein analogy is fundamental. The immunoglobulin-like fold may represent a robust system within which to examine again the issue of protein homology versus analogy.

Intrinsic disorder in scaffold proteins: getting more from less

Regulation, recognition and cell signaling involve the coordinated actions of many players. Signaling scaffolds, with their ability to bring together proteins belonging to common and/or interlinked pathways, play crucial roles in orchestrating numerous events by coordinating specific interactions among signaling proteins. This review examines the roles of intrinsic disorder (ID) in signaling scaffold protein function. Several well-characterized scaffold proteins with structurally and functionally characterized ID regions are used here to illustrate the importance of ID for scaffolding function. These examples include scaffolds that are mostly disordered, only partially disordered or those in which the ID resides in a scaffold partner. Specific scaffolds discussed include RNase, voltage-activated potassium channels, axin, BRCA1, GSK-3beta, p53, Ste5, titin, Fus3, BRCA1, MAP2, D-AKAP2 and AKAP250. Among the mechanisms discussed are: molecular recognition features, fly-casting, ease of encounter complex formation, structural isolation of partners, modulation of interactions between bound partners, masking of intramolecular interaction sites, maximized interaction surface per residue, toleration of high evolutionary rates, binding site overlap, allosteric modification, palindromic binding, reduced constraints for alternative splicing, efficient regulation via posttranslational modification, efficient regulation via rapid degradation, protection of normally solvent-exposed sites, enhancing the plasticity of interaction and molecular crowding. We conclude that ID can enhance scaffold function by a diverse array of mechanisms. In other words, scaffold proteins utilize several ID-facilitated mechanisms to enhance function, and by doing so, get more functionality from less structure.

Possible evolutionary links between immunoglobulin light chains and other proteins involved in amyloidosis

With limited exceptions, proteins that account for the amyloidoses appear to be evolutionarily unrelated. Transthyretin is classified as having an "immunoglobulin-like" fold as found in light chain variable and constant domains. Thus, these amyloidogenic proteins have significant conformational similarity. In the absence of primary structure similarity sufficient to justify an inference of an evolutionary relationship, transthyretin is considered an analog of immunoglobulin domains having accrued the immunoglobulin-like fold by some form of convergent evolution of structure. Improvements in sequence comparison tools and strategies, coupled with recent logarithmic increases in the availability of primary structure data, now make it possible to suggest that transthyretin and immunoglobulins may have a common evolutionary origin. In addition, lactadherin, the medin fragment of which accounts for the most common form of human amyloid, also appears to be evolutionarily linked to transthyretin and immunoglobulins.