Species‐dependent microarchitectural traits of iridescent scales in the triad taxa of Ornithoptera birdwing butterflies

Ornithoptera birdwing butterflies have blue, green, or orange iridescent scales in different species or subspecies. To understand the species‐ or subspecies‐dependent scale color differences, we performed comparative morphometric analyses of iridescent scales from three closely related taxa: O. priamus priamus (green), O. priamus urvillianus (blue), and O. croesus (orange). The three types of Ornithoptera wings exhibited reversible color changes to longer wavelengths with different kinetics upon immersion in methanol, suggesting that their color differences are at least partly based on differences in the size of air cavities made by nanostructures. Cover scales of all three color types were visually semi‐transparent glass scales that exhibited color when placed on a dark background. The dorsoventral differences in coloration were observed in single scales, suggesting the optical importance of scale surfaces. Scanning electron microscopy of cover scales in cross section revealed that all color types exhibited finely sculpted tapered ridges and thick, irregular basal multilayers containing tandemly clustered granular objects and air cavities. Scale thickness, ridge height, and multilayer thickness were significantly different among the three color types, and granular object size was significantly different between orange scales and blue and green scales. We conclude that each of the three taxa of Ornithoptera butterflies possesses unique quantitative size values on tapered ridges and irregular multilayers with granular objects and air cavities to express unique structural color. These species‐ or subspecies‐dependent structural colors might have evolved via quantitative shifts in these microarchitectural traits rather than via changes in the basic developmental or architectural plan for color expression.     

Biochemical characterization and structural insight into aliphatic β‐amino acid adenylation enzymes IdnL1 and CmiS6

Macrolactam antibiotics such as incednine and cremimycin possess an aliphatic β‐amino acid as a starter unit of their polyketide chain. In the biosynthesis of incednine and cremimycin, unique stand‐alone adenylation enzymes IdnL1 and CmiS6 select and activate the proper aliphatic β‐amino acid as a starter unit. In this study, we describe the enzymatic characterization and the structural basis of substrate specificity of IdnL1 and CmiS6. Functional analysis revealed that IdnL1 and CmiS6 recognize 3‐aminobutanoic acid and 3‐aminononanoic acid, respectively. We solved the X‐ray crystal structures of IdnL1 and CmiS6 to understand the recognition mechanism of these aliphatic β‐amino acids. These structures revealed that IdnL1 and CmiS6 share a common recognition motif that interacts with the β‐amino group of the substrates. However, the hydrophobic side‐chains of the substrates are accommodated differently in the two enzymes. IdnL1 has a bulky Leu220 located close to the terminal methyl group of 3‐aminobutanoate of the trapped acyl‐adenylate intermediate to construct a shallow substrate‐binding pocket. In contrast, CmiS6 possesses Gly220 at the corresponding position to accommodate 3‐aminononanoic acid. This structural observation was supported by a mutational study. Thus, the size of amino acid residue at the 220 position is critical for the selection of an aliphatic β‐amino acid substrate in these adenylation enzymes. Proteins 2017; 85:1238–1247. © 2017 Wiley Periodicals, Inc.     

Catalytic chemistry of solid polyoxometalates and their industrial applications

First, fundamental properties (structure, acid and redox properties) and advantages of solid polyoxometalate catalysts (catalyst design by acid and redox control, molecularity, unusual reaction field and unique basicity) are explained. Then, the mechanism of alcohol dehydration elucidated by direct observation of reaction intermediates by solid-state NMR and the very high activity of Cs_2.5H_0.5PW₁₂O₄₀ are described. Finally several industrial applications of polyoxometalate catalysts are briefly introduced placing stress on the role of unique chemical properties of polyoxometalates.     

Motor-Substrate Interactions in Mycoplasma Motility Explains Non-Arrhenius Temperature Dependence

Mycoplasmas exhibit a novel, substrate-dependent gliding motility that is driven by ∼400 “leg” proteins. The legs interact with the substrate and transmit the forces generated by an assembly of ATPase motors. The velocity of the cell increases linearly by nearly 10-fold over a narrow temperature range of 10-40°C. This corresponds to an Arrhenius factor that decreases from ∼45 k_BT at 10°C to ∼10 k_BT at 40°C. On the other hand, load-velocity curves at different temperatures extrapolate to nearly the same stall force, suggesting a temperature-insensitive force-generation mechanism near stall. In this article, we propose a leg-substrate interaction mechanism that explains the intriguing temperature sensitivity of this motility. The large Arrhenius factor at low temperature comes about from the addition of many smaller energy barriers arising from many substrate-binding sites at the distal end of the leg protein. The Arrhenius dependence attenuates at high temperature due to two factors: 1), the reduced effective multiplicity of energy barriers intrinsic to the multiple-site binding mechanism; and 2), the temperature-sensitive weakly facilitated leg release that curtails the power stroke. The model suggests an explanation for the similar steep, sub-Arrhenius temperature-velocity curves observed in many molecular motors, such as kinesin and myosin, wherein the temperature behavior is dominated not by the catalytic biochemistry, but by the motor-substrate interaction.     

The Amount of Metabolizable Glycine

Two roosters of Single Comb White Leghorn breed were fed on a formula feed containing 2-¹⁴C glycine for 16~17 days. The animals were killed and the specific activities of glycine in the tissue proteins and the purine ring of the excreted uric acid were measured. The amount of synthesized glycine in the rooster was calculated by the dilution method based on the specific activities of glycine in the liver protein and the absorbed one. The rooster absorbed about 1 g of glycine and synthesized about 10 g of glycine per day. Quantitative aspect of glycine metabolism in the rooster was discussed.     

Changes in Targeting Efficiencies of Proteins to Plant Microbodies Caused by Amino Acid Substitutions in the Carboxy-terminal Tripeptide

It has been demonstrated that the carboxyl terminus of microbodyenzymes functions as a targeting signal to microbodies in higherplants. We have examined an ability of 24 carboxy-terminal aminoacid sequences to facilitate the transport of a cytosolic passengerprotein, ß-glucuroni-dase, into microbodies in greencotyledonary cells of trans-genic Arabidopsis. Immunoelectronmicroscopic analysis revealed that carboxy-terminal tripeptidesequences of the form [C/A/S/P]-[K/R]-[I/L/M] function as amicrobody-targeting signal, although tripeptides with prolineat the first amino acid position and isoleucine at the carboxylterminus show weak targeting efficiencies. All known micro-bodyenzymes that are synthesized in a form similar in size to themature molecule, except catalase, contain one of these tripeptidesequences at their carboxyl terminus. (Received April 14, 1997; Accepted April 8, 1997)     

Studies on the Metabolic Activity of Muscle Proteins

The activities of glutamic oxaloacetic transaminase and Ca⁺⁺ ion-activated ATPase of muscle in the adult rats fed a protein-free diet for 8, 16 and 24 days were measured in order to clarify their metabolic responses with respect to reserve proteins. It was found that these enzyme activities, or presumably their enzyme proteins, decreased at the stage as early as the 8th day of protein depletion following the same pattern as seen in reserve proteins. Their responses, particularly those in unit activity, were somewhat different from each other. The metabolic significance of those responses was discussed in relation to protein nutrition.