Remodeling and activation mechanisms of outer arm dyneins revealed by cryo‐EM

Cilia are thin microtubule‐based protrusions of eukaryotic cells. The swimming of ciliated protists and sperm cells is propelled by the beating of cilia. Cilia propagate the flow of mucus in the trachea and protect the human body from viral infections. The main force generators of ciliary beating are the outer dynein arms (ODAs) which attach to the doublet microtubules. The bending of cilia is driven by the ODAs'' conformational changes caused by ATP hydrolysis. Here, we report the native ODA complex structure attaching to the doublet microtubule by cryo‐electron microscopy. The structure reveals how the ODA complex is attached to the doublet microtubule via the docking complex in its native state. Combined with coarse‐grained molecular dynamic simulations, we present a model of how the attachment of the ODA to the doublet microtubule induces remodeling and activation of the ODA complex.     

Distinct ecological niches of marine symbiotic N2‐fixing cyanobacterium Candidatus Atelocyanobacterium thalassa sublineages

A recently described symbiosis between the metabolically streamlined nitrogen‐fixing cyanobacterium UCYN‐A and a single‐celled eukaryote prymnesiophyte alga is widely distributed throughout tropical and subtropical marine waters, and is thought to contribute significantly to nitrogen fixation in these regions. Several UCYN‐A sublineages have been defined based on UCYN‐A nitrogenase (nifH) sequences. Due to the low abundances of UCYN‐A in the global oceans, currently existing molecular techniques are limited for detecting and quantifying these organisms. A targeted approach is needed to adequately characterize the diversity of this important marine cyanobacterium, and to advance understanding of its ecological importance. We present findings on the distribution of UCYN‐A sublineages based on high throughput sequencing of UCYN‐A nifH PCR amplicons from 78 samples distributed throughout many major oceanic provinces. These UCYN‐A nifH fragments were used to define oligotypes, alternative taxonomic units defined by nucleotide positions with high variability. The data set was dominated by a single oligotype associated with the UCYN‐A1 sublineage, consistent with previous observations of relatively high abundances in tropical and subtropical regions. However, this analysis also revealed for the first time the widespread distribution of the UCYN‐A3 sublineage in oligotrophic waters. Furthermore, distinct assemblages of UCYN‐A oligotypes were found in oligotrophic and coastally influenced waters. This unique data set provides a framework for determining the environmental controls on UCYN‐A distributions and the ecological importance of the different sublineages.     

Screening,identification, and characterization of a novel saccharide-stimulated β-glycosidase from a soil metagenomic library

Applied Microbiology and Biotechnology - MeBglD2, a β-glycosidase that is highly activated in the presence of various monosaccharides and disaccharides, was isolated from a soil metagenomic...     

Synthesis of alpha-lactosyl-(1-->3)-L-glycero-alpha-D-manno-heptopyranoside, a partial oligosaccharide structure expressed within the lipooligosaccharide produced by Neisseria gonorrhoeae strain 15253.

The glycosyl donor, hepta-O-benzyl-beta-lactosyl trichloroacetimidate (4) was prepared by treating hepta-O-benzyl-lactose with trichloroacetonitrile in the presence of potassium carbonate. The acceptor, methyl 2-O-benzyl-4,6-O-benzylidene-7,8-dideoxy-alpha-D-manno-oct-7-enopyranoside (8) was synthesized by hydrolysis of a 3,4-butane diacetal of methyl L-glycero-alpha-D-manno-oct-enopyranoside and subsequent benzylidenation. Glycosidation of the donor 4 with the acceptor 8 in 1,4-dioxane using Me(3)SiOTf as a promoter for 1 h at room temperature gave methyl (2,3,4,6-tetra-O-benzyl-beta-D-galactopyranosyl)-(1-->4)-(2,3,6-tri-O-benzyl-alpha-D-glucopyranosyl)-(1-->3)-2-O-benzyl-4,6-O-benzylidene-7,8-dideoxy-alpha-D-manno-oct-7-enopyranoside (9) as a major product (59%). The oct-enopyranoside moiety of the trisaccharide 9 was converted to a heptopyranoside (80%) by oxidative cleavage with OsO(4)-NaIO(4) and subsequent reduction. Hydrogenolysis of the resulting trisaccharide and subsequent acetylation gave the peracetate of alpha-lactosyl-(1-->3)-Hep. Deacetylation of the peracetate afforded the title trisaccharide.     

Stability of the O-octanoyl group of rat ghrelin during chemical synthesis: Counter-ion-dependent alteration of an ester bond breakage

Summary Rat ghrelin, a 28-amino acid residue peptide with an octanoyl group at the side chain of Ser3, was synthesized chemically by applying Fmoc/ ^t Bu strategy. An ester linkage between octanoic acid and the hydroxyl function of Ser3 was found to be maintained without serious damage during the final deprotection with trifluoroacetic acid (TFA). The most notable finding was the counter-ion-dependent stability change of the octanoyl moiety in the molecule. After consolidation of the counter-ion to TFA (TFA form), the octanoyl group persisted stably upon dissolution in water, whereas in the case of the acetate-form peptide, both de-octanoylation and dehydration (formation of the dehydro-Ala residue) occurred in aqueous solution at the same Ser3 residue. The amounts of these degraded products varied with factors such as solvent, temperature and times of lyophilization. These experimental findings lay the basis for performing the bioassay of ghrelin, which has an octanoyl moiety involved in its numerous biological activities thus far revealed.     

A case of hyperlipidemia with homozygous apolipoprotein E5 (Glu3→Lys)

In this study, we present clinical feature of a novel case with homozygous apolipoprotein (apo) E5.The patient was a 53-year-old Japanese woman. She was from a small island off the coast of Kagoshima Prefecture, Japan. Her parents were first degree cousins. No corneal opacification, xanthomatosis, lymphadenopathy, or hepatosplenomegaly was observed. There have been no signs of clinically overt atherosclerosis to date. Her serum total cholesterol, triglycerides (TG) and high-density lipoprotein (HDL)-cholesterol levels were 11.6, 6.1 and 1.2 mmol/l, respectively, and apo A-I, A-II, B, C-II, C-III and E levels were 121, 34.8, 269, 10.4, 25.7 and 10.3 mg/dl, respectively. Serum lipoprotein profile analyzed by agarose gel electrophoresis and differential staining revealed markedly increased cholesterol and TG in both β and preβ-migrated lipoproteins, whereas α-migrated lipoprotein showed decreased cholesterol. Her apo E isoform analyzed by isoelectric focusing (IEF) was found to be homozygous apo E5.Polymerase chain reaction restriction fragment length polymorphism (PCR-RFLP) analysis of her apo E and lipoprotein lipase (LPL) genes revealed that she had a homozygous apo E (Glu³→Lys) and heterozygous LPL variant Ser⁴⁴⁷ to Ter. Her son and daughter, both of whom had hyperlipidemia, were found to have apo E3/5 phenotype. Direct sequencing analysis of her apo E gene confirmed a homozygous one nucleotide change: G to A at nucleotide position of 2836 in the exon 3, resulting in Glu³→Lys mutation.This is the first report of lipids and lipoprotein profiles in patients with homozygous apo E5 (Glu³→Lys).