Structural insights into antigen recognition of an anti-β-(1,6)-β-(1,3)-D-glucan antibody.

Schizophyllan (SCH) is a high molecular weight homopolysaccharide composed of a β-(1,3)-D-glucan main chain with branching β-(1,6)-bound D-glucose residues. It forms triple helices that are highly stable towards heat and extreme pH, which provides SCH with interesting properties for industrial and medical applications. The recombinant anti-SCH antibody JoJ48C11 recognizes SCH and related β-(1,6)-branched β-(1,3)-D-glucans, but details governing its specificity are not known.

Insights into the Dual Activity of a Bifunctional Dehydratase-Cyclase Domain.

Oxygen-containing heterocycles are a common structural motif in polyketide natural products and contribute significantly to their biological activity. Here, we report structural and mechanistic investigations on AmbDH3, a polyketide synthase domain with dual activity as dehydratase (DH) and pyran-forming cyclase in ambruticin biosynthesis. AmbDH3 is similar to monofunctional DH domains, using H51 and D215 for dehydration.

Direct recognition of the C-terminal polylysine residues of nonstop protein by Ltn1, an E3 ubiquitin ligase.

When mRNAs lack stop codons, errors in gene expression and coding of aberrant proteins that are harmful in cells can result. In Saccharomyces cerevisiae, a 180-kDa E3-ubiquitin ligase, Ltn1 has been known to associate with ribosomes and marks translationally-arrested aberrant nascent polypeptides for proteasomal degradation. Here, we demonstrate the Ltn1 E3-ubiquitin ligase directly binds to the nonstop proteins and efficiently ubiquitylates them.

Insights into the molecular evolution of HslU ATPase through biochemical and mutational analyses.

The ATP-dependent HslVU complexes are found in all three biological kingdoms. A single HslV protease exists in each species of prokaryotes, archaea, and eukaryotes, but two HslUs (HslU1 and HslU2) are present in the mitochondria of eukaryotes. Previously, a tyrosine residue at the C-terminal tail of HslU2 has been identified as a key determinant of HslV activation in Trypanosoma brucei and a phenylalanine at the equivalent position to E.

Structural and biochemical analyses of the eukaryotic heat shock locus V (HslV) from Trypanosoma brucei.

In many bacteria, heat shock locus V (HslV) functions as a protease, which is activated by heat shock locus U (HslU). The primary sequence and structure of HslV are well conserved with those of the β-subunit of the 20 S proteasome core particle in eukaryotes. To date, the HslVU complex has only been characterized in the prokaryotic system.

Structures of ClpP in complex with acyldepsipeptide antibiotics reveal its activation mechanism.

Clp-family proteins are prototypes for studying the mechanism of ATP-dependent proteases because the proteolytic activity of the ClpP core is tightly regulated by activating Clp-ATPases. Nonetheless, the proteolytic activation mechanism has remained elusive because of the lack of a complex structure. Acyldepsipeptides (ADEPs), a recently discovered class of antibiotics, activate and disregulate ClpP.

Outbreaks of imipenem-resistant Acinetobacter baumannii producing carbapenemases in Korea.

Among 53 Acinetobacter baumannii isolates collected in 2004, nine imipenem-resistant isolates were obtained from clinical specimens taken from patients hospitalized in Busan, Korea. Nine carbapenemase-producing isolates were further investigated in order to determine the mechanisms underlying resistance. These isolates were then analyzed via antibiotic susceptibility testing, microbiological tests of carbapenemase activity, pI determination, transconjugation test, enterobacterial repetitive consensus (ERIC)-PCR, and DNA sequencing.