Configuration-Specific Antibody for Bacterial Heptosylation: An Antiadhesion Therapeutic Strategy.

Alternative antibacterial therapies refractory to existing mechanisms of antibiotic resistance are urgently needed. One such attractive therapy is to inhibit bacterial adhesion and colonization. Ser O-heptosylation (Ser O-Hep) on autotransporters of Gram-negative bacteria is a novel glycosylation and has been proven to be essential for bacterial colonization. Herein, we chemically synthesized glycopeptides containing this atypical glycan structure and an absolute C6 configuration through the assembly of Ser O-Hep building blocks. Using glycopeptides as haptens, we generated first-in-class poly- and monoclonal antibodies, termed Anti-SerHep1a and Anti-SerHep1b, that stereoselectively recognize Ser O-heptosylation (d/l-glycero) with high specificity in vitro and in vivo. Importantly, these antibodies effectively blocked diffusely adhering Escherichia coli 2787 adhesion to HeLa cells and in mice in a dose- and Ser O-Hep-dependent manner. Together, these antibodies represent not only useful tools for the discovery of unknown serine O-heptosylated proteins bearing various C6 chiral centers but also a novel class of antiadhesion therapeutic agents for the treatment of bacterial infection.

[Cloning and analysis of genes in the halocin C8 gene cluster].

Halocin C8 (HalC8), produced by a halophilic archaeon strain AS7092, is a gene-coded peptide microhalocin and has a wide inhibitory spectrum against the members of haloarchaea. To investigate the mechanisms of the gene expression regulation, the peptide processing and transportation of this halocin, a 9.3kb DNA gene cluster containing the halocin C8 encoding gene (proC8) and other possible involved genes was cloned, by screening of a genomic library of AS7092 as well as anchoring PCR technique. Sequence analysis indicated that it contained at least six open reading frames, including halU, halR, proC8, halT1, halT2 and halT3. The gene halU encodes a membrane-spanning protein HalU, but its function is unknown. The gene halR encodes a putative regulator protein HalR, its function was deduced to regulate the transcription of proC8 gene, which encodes the precursor for halocin C8. The gene halT1, halT2 and halT3 likely encode the transporters HalT1, HalT2 and HalT3, the functions of which were speculated to transport the halocin C8 out of the cellular membrane. This is the first report of gene cluster cloning for any halocin.