Highly probable active site of the sweet protein monellin.

The sweet protein monellin consists of two noncovalently associated polypeptide chains, the A chain of 44 amino acid residues and the B chain of 50 residues. Synthetic monellin is 4000 times as sweet as sucrose on a weight basis, and the native conformation is essential for the sweet taste. Knowledge of the active site of monellin will provide important information on the mode of interaction between sweeteners and their receptors. If the replacement of a certain amino acid residue in monellin removes the sweet taste, while the native conformation is retained, it may be concluded that the position replaced is the active site. Our previous replacement studies on Asp residues in the A chain did not remove the sweet taste. The B chain contains two Asp residues at positions 7 and 21, which were replaced by Asn. [AsnB21]Monellin and [AsnB7]monellin were 7000 and 20 times sweeter than sucrose, respectively. The low potency of the [AsnB7]monellin indicates that AspB7 participates in binding with the receptor. AspB7 was then replaced by Abu. [AbuB7]Monellin was devoid of sweetness, and retained the native conformation. AspB7 is located at the surface of the molecule (Ogata et al.). These results suggest that Asp7 in the B chain is the highly probable active site of monellin.     

Atomic structure of a pyrimidine-dimer specific excision-repair enzyme from bacteriophage T4.

T4 endonuclease V is an enzyme responsible for the first step of a pyrimidine-dimer specific excision-repair process. The three-dimensional structure of this enzyme has been determined at 1.6A resolution by X-ray crystallography. The enzyme consists of one single compact domain classified into the all alpha structure. This single domain possesses two distinct catalytic activities, a pyrimidine-dimer glycosylase and an apurinic/apyrimidinic endonuclease. The backbone of the enzyme represents a unique folding scheme incompatible with close packing of alpha-helices. The refined structure suggests possible residues that participate in interactions with DNA.     

Cryo‐EM structure of the CENP‐A nucleosome in complex with phosphorylated CENP‐C

The CENP‐A nucleosome is a key structure for kinetochore assembly. Once the CENP‐A nucleosome is established in the centromere, additional proteins recognize the CENP‐A nucleosome to form a kinetochore. CENP‐C and CENP‐N are CENP‐A binding proteins. We previously demonstrated that vertebrate CENP‐C binding to the CENP‐A nucleosome is regulated by CDK1‐mediated CENP‐C phosphorylation. However, it is still unknown how the phosphorylation of CENP‐C regulates its binding to CENP‐A. It is also not completely understood how and whether CENP‐C and CENP‐N act together on the CENP‐A nucleosome. Here, using cryo‐electron microscopy (cryo‐EM) in combination with biochemical approaches, we reveal a stable CENP‐A nucleosome‐binding mode of CENP‐C through unique regions. The chicken CENP‐C structure bound to the CENP‐A nucleosome is stabilized by an intramolecular link through the phosphorylated CENP‐C residue. The stable CENP‐A‐CENP‐C complex excludes CENP‐N from the CENP‐A nucleosome. These findings provide mechanistic insights into the dynamic kinetochore assembly regulated by CDK1‐mediated CENP‐C phosphorylation.     

Chromosomal assignment of a novel human gene D40.

We have previously reported an identification of a novel human cellular factor, D40. Here, we report the chromosomal localization of the gene that encodes D40. Fluorescent in situ hybridization (FISH) was performed to determine the chromosomal region that D40 gene resides. The chromosomes that derived from normal adult male lymphocytes were hybridized with a mixture of cDNA probes that cover the entire coding region of D40. D40 gene mapped to the long arm of chromosome 15q14-15.     

Resistance to the rice leaf bug, Trigonotylus caelestialium, is conferred by Neotyphodium endophyte infection of perennial ryegrass, Lolium perenne

Neotyphodium fungal endophytes form mutualistic symbiotic associations with many grasses of the subfamily Pooideae, including important forage and turfgrass species. This relationship provides a competitive advantage to the host plant by increasing abiotic/biotic stress tolerance, such as its resistance to drought, diseases, and insect pests. The insect deterrent effects of endophytes are now receiving attention in Japan, as insect pests growing in meadows are causing problems in adjacent rice paddies. One of the most serious problems is the kernel spotting of rice grains caused by the rice leaf bug, Trigonotylus caelestialium Kirkaldy (Heteroptera: Miridae), which reproduces on Lolium species grown as forage. To determine the potential of Neotyphodium endophytes to reduce the invasion of rice crops by T. caelestialium from adjacent Lolium crops, we carried out choice and no‐choice feeding tests using endophyte‐infected and endophyte‐free clonal perennial ryegrass (Lolium perenne L.) (Poaceae). Our experiments revealed that the presence of the Neotyphodium endophyte strongly deterred the feeding of both first‐instar larvae and adults of T. caelestialium. These results show the potential of Neotyphodium endophytes to reduce the number of T. caelestialium in forage fields and grasslands, and thus to reduce the damage to rice grains caused by this insect pest.     

Meningitis patients with Angiostrongylus cantonensis may present without eosinophilia in the cerebrospinal fluid in northern Vietnam

BackgroundEosinophilic meningitis (EM) is a rare clinical syndrome caused by both infectious and noninfectious diseases. In tropical pacific countries, Angiostrongylus cantonensis is the most common cause. However, the EM definition varies in the literature, and its relation to parasitic meningitis (PM) remains unclear.Methodology/Principal findingsAdult and adolescent patients of 13 years old or above with suspected central nervous system (CNS) infections with abnormal CSF findings were prospectively enrolled at a tertiary referral hospital in Hanoi, Vietnam from June 2012 to May 2014. Patients with EM or suspected PM (EM/PM) were defined by the presence of either ≥10% eosinophils or an absolute eosinophil cell counts of ≥10/mm³ in the CSF or blood eosinophilia (>16% of WBCs) without CSF eosinophils. In total 679 patients were enrolled: 7 (1.03%) had ≥10% CSF eosinophilia, 20 (2.95%) had ≥10/mm³ CSF eosinophilia, and 7 (1.03%) had >16% blood eosinophilia. The patients with ≥10% CSF eosinophilia were significantly younger (p = 0.017), had a lower body temperature (p = 0.036) than patients with ≥10/mm³ CSF eosinophilia among whom bacterial pathogens were detected in 72.2% (13/18) of those who were tested by culture and/or PCR. In contrast, the characteristics of the patients with >16% blood eosinophilia resembled those of patients with ≥10% CSF eosinophilia. We further conducted serological tests and real-time PCR to identify A. cantonensis. Serology or real-time PCR was positive in 3 (42.8%) patients with ≥10% CSF eosinophilia and 6 (85.7%) patients with >16% blood eosinophilia without CSF eosinophils but none of patients with ≥10/mm³ CSF eosinophilia.ConclusionsThe etiology of PM in northern Vietnam is A. cantonensis. The eosinophil percentage is a more reliable predictor of parasitic EM than absolute eosinophil count in the CSF. Patients with PM may present with a high percentage of eosinophils in the peripheral blood but not in the CSF.     

Genetic population structure of the eight-barbel loach Lefua echigonia in the Ise Bay region,a single paleo-river basin in central Honshu,Japan

Ichthyological Research - We examined the genetic population structure of Lefua echigonia in the Ise Bay region based on the nucleotide sequences of the mitochondrial DNA cytochrome b region....