Identification of the potential active site of the septal peptidoglycan polymerase FtsW

SEDS (Shape, Elongation, Division and Sporulation) proteins are widely conserved peptidoglycan (PG) glycosyltransferases that form complexes with class B penicillin-binding proteins (bPBPs, with transpeptidase activity) to synthesize PG during bacterial cell growth and division. Because of their crucial roles in bacterial morphogenesis, SEDS proteins are one of the most promising targets for the development of new antibiotics. However, how SEDS proteins recognize their substrate lipid II, the building block of the PG layer, and polymerize it into glycan strands is still not clear. In this study, we isolated and characterized dominant-negative alleles of FtsW, a SEDS protein critical for septal PG synthesis during bacterial cytokinesis. Interestingly, most of the dominant-negative FtsW mutations reside in extracellular loops that are highly conserved in the SEDS family. Moreover, these mutations are scattered around a central cavity in a modeled FtsW structure, which has been proposed to be the active site of SEDS proteins. Consistent with this, we found that these mutations blocked septal PG synthesis but did not affect FtsW localization to the division site, interaction with its partners nor its substrate lipid II. Taken together, these results suggest that the residues corresponding to the dominant-negative mutations likely constitute the active site of FtsW, which may aid in the design of FtsW inhibitors.

Dental abnormalities in a patient with autosomal dominant hyper-IgE syndrome: A case control study

Autosomal-dominant hyper-IgE (AD-HIES) is mainly characterized by eczematous dermatitis, staphylococcal skin abscesses, connective tissue defects, and elevated serum IgE. This disorder is largely associated with heterozygous dominant-negative mutations in STAT3 gene. Herein, we reported a patient with AD-HIES suffering from dental abnormality and allergic reactions.

Current Perspective on Dominant Negative Mutations: Trends, Scope and Relevance

Despite the advancements in tools and technologies implicated in identifying and characterizing novel genes, there are still a significant number of unknown function proteins. Moreover, the practices employed in order to characterize such proteins have proven to be a futile exercise so far because of many limitations associated with such traditional approaches. Dominant-negative mutations have shown great promise in this direction as the introduction of mutation in the target protein may abolish the protein function and inhibit the function of the simultaneously expressed wild-type protein. These dominant mutations have broader applications in biological processes to study various proteins in terms of their functional aspects, etiological factors, and mechanism of action, paving the way to diagnose many dreadful diseases, including cancer. Considering these facts, the current review emphasizes utilizing the full potential of such dominant-negative mutations in deciphering protein functions and their broad-spectrum applications in biology.

Dominant-negative mutations in human IL6ST underlie hyper-IgE syndrome

Autosomal dominant hyper-IgE syndrome (AD-HIES) is typically caused by dominant-negative (DN) STAT3 mutations. Patients suffer from cold staphylococcal lesions and mucocutaneous candidiasis, severe allergy, and skeletal abnormalities. We report 12 patients from 8 unrelated kindreds with AD-HIES due to DN IL6ST mutations. We identified seven different truncating mutations, one of which was recurrent. The mutant alleles encode GP130 receptors bearing the transmembrane domain but lacking both the recycling motif and all four STAT3-recruiting tyrosine residues. Upon overexpression, the mutant proteins accumulate at the cell surface and are loss of function and DN for cellular responses to IL-6, IL-11, LIF, and OSM. Moreover, the patients’ heterozygous leukocytes and fibroblasts respond poorly to IL-6 and IL-11. Consistently, patients with STAT3 and IL6ST mutations display infectious and allergic manifestations of IL-6R deficiency, and some of the skeletal abnormalities of IL-11R deficiency. DN STAT3 and IL6ST mutations thus appear to underlie clinical phenocopies through impairment of the IL-6 and IL-11 response pathways.