Crystal structure of Grimontia hollisae collagenase provides insights into its novel substrate specificity toward collagen

Collagenase from the gram-negative bacterium Grimontia hollisae strain 1706B (Ghcol) degrades collagen more efficiently even than clostridial collagenase, the most widely used industrial collagenase. However, the structural determinants facilitating this efficiency are unclear. Here, we report the crystal structures of ligand-free and Gly-Pro-hydroxyproline (Hyp)-complexed Ghcol at 2.2 and 2.4 Å resolution, respectively. These structures revealed that the activator and peptidase domains in Ghcol form a saddle-shaped structure with one zinc ion and four calcium ions. In addition, the activator domain comprises two homologous subdomains, whereas zinc-bound water was observed in the ligand-free Ghcol. In the ligand-complexed Ghcol, we found two Gly-Pro-Hyp molecules, each bind at the active site and at two surfaces on the duplicate subdomains of the activator domain facing the active site, and the nucleophilic water is replaced by the carboxyl oxygen of Hyp at the P1 position. Furthermore, all Gly-Pro-Hyp molecules bound to Ghcol have almost the same conformation as Pro-Pro-Gly motif in model collagen (Pro-Pro-Gly)₁₀, suggesting these three sites contribute to the unwinding of the collagen triple helix. A comparison of activities revealed that Ghcol exhibits broader substrate specificity than clostridial collagenase at the P2 and P2′ positions, which may be attributed to the larger space available for substrate binding at the S2 and S2′ sites in Ghcol. Analysis of variants of three active-site Tyr residues revealed that mutation of Tyr564 affected catalysis, whereas mutation of Tyr476 or Tyr555 affected substrate recognition. These results provide insights into the substrate specificity and mechanism of G. hollisae collagenase

Synthesis of donor–acceptor chromophores by the [2 + 2] cycloaddition of arylethynyl-2H-cyclohepta[b]furan-2-ones with 7,7,8,8-tetracyanoquinodimethane

Arylethynyl-2H-cyclohepta[b]furan-2-ones reacted with 7,7,8,8-tetracyanoquinodimethane (TCNQ) in a formal [2 + 2] cycloaddition reaction, followed by ring opening of the initially formed cyclobutene derivatives, to afford the corresponding dicyanoquinodimethane (DCNQ) chromophores in excellent yields. The intramolecular charge-transfer (ICT) interactions between the 2H-cyclohepta[b]furan-2-one ring and DCNQ acceptor moiety were investigated by UV/Vis spectroscopy and theoretical calculations. The redox behavior of the novel DCNQ derivatives was examined by cyclic voltammetry (CV) and differential pulse voltammetry (DPV), which revealed their multistep electrochemical reduction properties depended on the number of DCNQ units in the molecule. Moreover, a significant color change was observed by visible spectroscopy under electrochemical reduction conditions.ArticleORGANIC & BIOMOLECULAR CHEMISTRY. 10(12):2431-2438 (2012)journal articl

Successful Transanal Removal of a Rectal Foreign Body by Abdominal Compression under Endoscopic and X-Ray Fluoroscopic Observation: A Case Report

We occasionally encounter patients with various types of rectal foreign bodies. When too large to grasp, transanal removal can be difficult. Here, we report a case of successful manual transanal removal of an 18 × 4 × 4 cm silicon rod without complications. A 50-year-old male came to the emergency department of our hospital 12 h after transanal insertion of a whole silicon rod. An abdominal examination showed no evidence of peritonitis, while X-ray and computed tomography findings revealed a large foreign body in the rectum, without any sign of perforation. Initially, we attempted removal using an endoscopy procedure with conventional endoscopic instruments, including a snare and grasp forceps, though we failed because of the large size. Next, we manually compressed the foreign body from the abdominal wall under endoscopic and X-ray fluoroscopic observation, and successfully removed it in a transanal manner without complications. Endoscopic and X-ray fluoroscopic assistance were helpful to guide the direction and angle of abdominal compression in this case

Isolated Superior Mesenteric Artery Dissection with Small Intestine Ischemia

Superior mesenteric artery (SMA) dissection without aortic dissection is a rare condition, and its diagnosis is considered to be difficult. Intestinal infarction is a severe complication of the disease, which may require resection of the intestine. We present a case of isolated SMA dissection. A 53-year-old man experienced sudden pain in the abdomen while playing Japanese pinball and was admitted to our hospital due to acute abdominal symptoms of uncertain cause. Enhanced CT revealed a defect of the root of the SMA, while angiography and intravascular ultrasound findings showed dissection of the SMA wall. Conservative treatment was chosen at the time, while a part of the small intestine was eventually resected because of progressive ischemia. Although SMA dissection is a rare occurrence in cases with acute abdominal symptoms, awareness of the condition is important for differential diagnosis