Structure function and engineering of multifunctional non-heme iron dependent oxygenases in fungal meroterpenoid biosynthesis

Non-heme iron and α-ketoglutarate (αKG) oxygenases catalyze remarkably diverse reactions using a single ferrous ion cofactor. A major challenge in studying this versatile family of enzymes is to understand their structure–function relationship. AusE from Aspergillus nidulans and PrhA from Penicillium brasilianum are two highly homologous Fe(II)/αKG oxygenases in fungal meroterpenoid biosynthetic pathways that use preaustinoid A1 as a common substrate to catalyze divergent rearrangement reactions to form the spiro-lactone in austinol and cycloheptadiene moiety in paraherquonin, respectively. Herein, we report the comparative structural study of AusE and PrhA, which led to the identification of three key active site residues that control their reactivity. Structure-guided mutagenesis of these residues results in successful interconversion of AusE and PrhA functions as well as generation of the PrhA double and triple mutants with expanded catalytic repertoire. Manipulation of the multifunctional Fe(II)/αKG oxygenases thus provides an excellent platform for the future development of biocatalysts.

Non-heme iron and α-ketoglutarate (αKG) oxygenases play a major role in fungal meroterpenoid biosynthesis, but their mechanism remains elusive. Here the authors present crystal structures of two oxygenases, AusE and PrhA, which provide insights into the multifunctional nature of these enzymes.

Effective Production of Aromatic Polyketides in Streptomyces using a Combined-Culture Method

Combinedculture is a fermentation method which efficiently induces secondary metabolite production in Streptomyces by co-culturing them with mycolic acid-containing bacteria. As a result of combined-culture screening -of our terrestrial Streptomyces collection using UV-HPLC, one of the tested strains, Streptoinyces. sp. TAKO-2, produced two known aromatic polyketides, julichrome Q6 (1) and julichrome Q₈.₈ (2), when co-cultured with the mycolic acid- containing bacterium Tsukamurella pulmonis TP-B0596. The structures of 1 and 2 were confirmed by spectroscopic analysis and literature data.

Effective Production of Aromatic Polyketides in Streptomyces using a Combined-Culture Method

Combined-culture is a fermentation method which efficiently induces secondary metabolite production in Streptomyces by co-culturing them with mycolic acid-containing bacteria. As a result of combined-culture screening of our terrestrial Streptomyces collection using UV-HPLC, one of the tested strains, Streptomyces sp. TAKO-2, produced two known aromatic polyketides, julichrome Q6 (1) and julichrome Q8·8 (2), when co-cultured with the mycolic acid-containing bacterium Tsukamurella pulmonis TP-B0596. The structures of 1 and 2 were confirmed by spectroscopic analysis and literature data.

Angioscopic External Valvuloplasty in the Treatment of Varicose Veins

Objective:

To report on the surgical treatment of varicose veins by angioscopic valvuloplasty to preserve the long saphenous vein (LSV) and the efficacy of this method compared with conventional stripping and high ligation.

Methods:

A total of 306 limbs in 187 patients with reflux at the sapheno-femoral junction to below knee level were operated on using intraoperative angioscopy to diagnose valve insufficiency. Angioscopic external valvuloplasty was attempted for the subterminal valves in the LSV by three techniques: total plication of the dilated annulus by running polypropylene sutures (technique 1), plication by autogenous femorofascial sleeve or Dacron-reinforced silicone (technique 2), and plication of the commissure with shortening of the cusps from outside the vein wall (technique 3). Partial stripping or segmental ligation was performed for varicose veins below knee level and the incompetent perforating veins were treated simultaneously by suprafascial ligation.

Results:

The subterminal valves were classified as follows: valves with elongated and atrophic cusps – type I, 136 (44%); valves with expanded and depressed commissures with cusp changes – type II, 108 (35%); valves that had cusps with other deformities – type III, 38 (13%); and absence of valves between the saphenofemoral junction and mid-thigh level, 24 limbs (8%). Valvuloplasty of the LSV was successfully performed in 62 limbs (20%). There were two cases with occlusion of the LSV (3%) and four with recurrence of varicose veins (6%) at 2–89 (mean 55, SD 21) months follow-up.

Conclusions:

Angioscopic external valvuloplasty is effective in the treatment of varicose veins to preserve the LSV. Further data are needed for complete evaluation of this procedure.

The Appearance of Cytokines and Adhesion Molecules in Saphenous Vein Valves in Chronic Venous Insufficiency

Objective:

To evaluate the difference between competent valves and incompetent valves with regards to the development of expression of cytokines and adhesion molecules in primary varicose veins.

Methods:

Specimens were obtained from 13 patients with primary varicose veins during surgery. Valves were classified according to the angioscopic findings: 8 competent and 17 incompetent valves; type I (7 valves with elongated cusps) and type II (10 valves with expansion of commissures). The mRNA levels of interleukin-1β (IL-1β), interleukin-6 (IL-6), interleukin-8 (IL-8), tumour necrosis factor-α (TNF-α), transforming growth factor-β (TGF-β), intercellular adhesion molecule-1 (ICAM-1), vascular cell adhesion molecule-1 (VCAM-1) and endothelial leucocyte adhesion molecule-1 (ELAM-1) were measured by polymerase chain reaction (PCR) amplification of cDNA reverse-transcribed from RNAs.

Results:

In all cases there were few appearances of IL-6, IL-8 and TNF-α at the valve cusps. TGF-β and VCAM-1 levels were highly elevated in the cusps of incompetent valves compared with competent valves ( p<0.05). At the venous wall IL-6 and IL-8 occurred more frequently in incompetent valves than in competent valves ( p<0.05).

Conclusion:

This study suggests that inflammatory cytokines and adhesions molecules, especially TGF-β, IL-6, IL-8 and VCAM-1, may be related to the occurrence of valve insufficiency.

Manipulation of prenylation reactions by structure-based engineering of bacterial indolactam prenyltransferases

Prenylation reactions play crucial roles in controlling the activities of biomolecules. Bacterial prenyltransferases, TleC from Streptomyces blastmyceticus and MpnD from Marinactinospora thermotolerans, catalyse the ‘reverse' prenylation of (−)-indolactam V at the C-7 position of the indole ring with geranyl pyrophosphate or dimethylallyl pyrophosphate, to produce lyngbyatoxin or pendolmycin, respectively. Using in vitro analyses, here we show that both TleC and MpnD exhibit relaxed substrate specificities and accept various chain lengths (C₅–C₂₅) of the prenyl donors. Comparisons of the crystal structures and their ternary complexes with (−)-indolactam V and dimethylallyl S-thiophosphate revealed the intimate structural details of the enzyme-catalysed ‘reverse' prenylation reactions and identified the active-site residues governing the selection of the substrates. Furthermore, structure-based enzyme engineering successfully altered the preference for the prenyl chain length of the substrates, as well as the regio- and stereo-selectivities of the prenylation reactions, to produce a series of unnatural novel indolactams.

Regioselective prenylation of small aromatic natural molecules is crucial for their biological activity. Here, the authors present the biochemical and structural characterisation of two prenyltransferases and a structure-based engineering strategy to modulate their substrate specificity.

Niizalactams A-C, Multicyclic Macrolactams Isolated from Combined Culture of Streptomyces with Mycolic Acid-Containing Bacterium

A terrestrial bacterium, Streptomyces sp. NZ-6, produced niizalactams A-C (1-3), unprecedented di- and tricyclic macrolactams, by coculturing with the mycolic acid-containing bacterium Tsukamurella pulmonis TP-B0596. Their complete structures, including absolute configurations, were elucidated on the basis of spectroscopic data and chemical derivatization. Their unique skeletons are proposed to be biosynthesized from a common 26-membered macrolactam intermediate by SN2 cyclization or an intramolecular Diels-Alder reaction.

Characterization of anti-P monoclonal antibodies directed against the ribosomal protein-RNA complex antigen and produced using Murphy Roths large autoimmune-prone mice

Autoantibodies, including anti-ribosomal P proteins (anti-P), are thought to be produced by an antigen-driven immune response in systemic lupus erythematosus (SLE). To test this hypothesis, we reconstituted the ribosomal antigenic complex in vitro using human P0, phosphorylated P1 and P2 and a 28S rRNA fragment covering the P0 binding site, and immunized Murphy Roths large (MRL)/lrp lupus mice with this complex without any added adjuvant to generate anti-P antibodies. Using hybridoma technology, we subsequently obtained 34 clones, each producing an anti-P monoclonal antibody (mAb) that recognized the conserved C-terminal tail sequence common to all three P proteins. We also obtained two P0-specific monoclonal antibodies, but no antibody specific to P1, P2 or rRNA fragment. Two types of mAbs were found among these anti-P antibodies: one type (e.g. 9D5) reacted more strongly with the phosphorylated P1 and P2 than that with their non-phosphorylated forms, whereas the other type (e.g. 4H11) reacted equally with both phosphorylated and non-phosphorylated forms of P1/P2. Both 9D5 and 4H11 inhibited the ribosome/eukaryotic elongation factor-2 (eEF-2)-coupled guanosine triphosphate (GTP)ase activity. However, preincubation with a synthetic peptide corresponding to the C-terminal sequence common to all three P proteins, but not the peptide that lacked the last three C-terminal amino acids, mostly prevented the mAb-induced inhibition of GTPase activity. Thus, at least two types of anti-P were produced preferentially following the immunization of MRL mice with the reconstituted antigenic complex. Presence of multiple copies of the C-termini, particularly that of the last three C-terminal amino acid residues, in the antigenic complex appears to contribute to the immunogenic stimulus.

Variant parameter values-as defined by the Chicago Criteria-produced by ManoScan and a new system with Unisensor catheter

BACKGROUND

Recently reported normal values for esophageal motility obtained by high-resolution manometry (HRM) using a system with a Unisensor catheter were significantly different from those obtained by the ManoScan(®) , which could result in a wrong diagnosis. To clarify whether these differences were due to system or subject differences, we compared the manometric parameter values between ManoScan and a new system with a Unisensor catheter (Starlet) in the same subjects.

METHODS

A total of 103 volunteers without any symptoms related to esophageal motility disorders were recruited. Esophageal HRM was performed using both the ManoScan and the Starlet in all subjects. Data from the ManoScan were analyzed using ManoView, and data from the Starlet were analyzed by a program with e-sleeve function. Integrated relaxation pressure, distal contractile integral, contractile front velocity (CFV), intrabolus pressure, and distal latency were calculated by both analyzing programs, and the values of these parameters were compared between the two systems by a signed rank test.

KEY RESULTS

Data from a total of 97 participants were analyzed. The values of all parameters, except CFV, measured by the Starlet were significantly higher than those obtained by the ManoScan (p < 0.01).

CONCLUSIONS & INFERENCES

Both systems can measure esophageal motility appropriately; nevertheless, we confirmed that the two systems showed different values of the parameters defined by the Chicago criteria. These differences should be recognized to evaluate esophageal motility precisely.