Interactions of bacterial flagellar chaperone–substrate complexes with FlhA contribute to co‐ordinating assembly of the flagellar filament

Assembly of the bacterial flagellar filament is strictly sequential; the junction proteins, FlgK and FlgL, are assembled at the distal end of the hook prior to the FliD cap, which supports assembly of as many as 30 000 FliC molecules into the filament. Export of these proteins requires assistance of flagellar chaperones: FlgN for FlgK and FlgL, FliT for FliD and FliS for FliC. The C‐terminal cytoplasmic domain of FlhA (FlhA_C), a membrane component of the export apparatus, provides a binding‐site for these chaperone–substrate complexes but it remains unknown how it co‐ordinates flagellar protein export. Here, we report that the highly conserved hydrophobic dimple of FlhA_C is involved in the export of FlgK, FlgL, FliD and FliC but not in proteins responsible for the structure and assembly of the hook, and that the binding affinity of FlhA_C for the FlgN/FlgK complex is slightly higher than that for the FliT/FliD complex and about 14‐fold higher than that for the FliS/FliC complex, leading to the proposal that the different binding affinities of FlhA_C for these chaperone/substrate complexes may confer an advantage for the efficient formation of the junction and cap structures at the tip of the hook prior to filament formation.     

2-Nitropropane Dioxygenase from Hansenula mrakii: Re-characterization of the Enzyme and Oxidation of Anionic Nitroalkanes

2-Nitropropane dioxygenase, purified to homogeneity by an improved method from a yeast, Hansenula mrakii, has a molecular weight of 42,000, and consists of a single polypeptide. The enzyme contains 1 mol of FAD per mol of enzyme. The iron protein associated with previous preparations was removed by the present purification procedures. The enzyme catalyzes the oxygenative denitrification of anionic nitroalkanes much more effectively than that of the neutral ones with the optimum pH of 6.5. The Michaelis constants for the anionic substrates are as follows: 2-nitropropane, 1.61 mM; 1-nitropropane, 3.23 mM; nitroethane, 3.13 mM, and 3-nitro-2-butanol, 0.59 mM.     

Structures of Ezomycins A1 and A2

The structures of ezomycins A₁. and A₂, antifungal antibiotics produced by a strain of Streptomyces, were determined as 1 and 2, respectively, by degradative and spectrometric studies.     

Carboxyl Proteinase from the Wood Deteriorating Basidiomycete Pycnoporus coccineus :Substrate Specificity with Oxidized Insulin Peptide B1 ~ B16 and B15 ~ B24, Angiotensin and Proangiotensin

The specificity of highly purified carboxyl proteinase from Pycnoporus coccineus (formerly designated Trametes sanguined) was investigated with oligopeptides at pH 2.7. Hydrolysis of oxidized insulin peptide Bl ~ B16 was observed at two peptide bonds (His¹⁰-Leu¹¹ and Ala¹⁴-Leu¹⁵) during 3-hr incubation. The enzyme did not hydrolyze oxidized insulin peptide B15 ~ B24. Hydrolysis of angiotensin (formerly designated angiotensin II) was observed at the Tyr⁴-Ile⁵ bond. Hydrolysis of proangiotensin (formerly designated angiotensin I) was also at the Tyr⁴-Ile⁵ bond. In conclusion, peptide bonds which have a hydrophobic amino acid in the P′₁ position (as defined by Schechter and Berger, Biochem. Biophys. Res. Commun., 27, 157 (1967)) are preferentially cleaved by the trypsinogen activating carboxyl proteinase of Pycnoporus coccineus.     

Change of Freezing Resistance and Retention of Metabolic and Differentiation Potentials in Cultured Green Lavandula vera Cells Which Survived Repeated Freeze-thaw Procedures

Cryostorage is one suitable method to preserve various desired types of cells. However, all cells do not survive after storage in liquid nitrogen. This suggests the possibility that the properties of the cells which survive after the storage differ from those of the unfrozen original cells.

Therefore, we did the same freeze-thaw procedure of cultured green Lavandula vera cells over again and compared the metabolic and the differentiation potentials of the cells which survived after the repeated freeze-thaw procedures with those of the unfrozen original cells. The results we found were that the frequency of colony formation of the cells which survived after the procedures was high, but that the biosynthetic capability for biotin and the differentiation potentials such as chloroplast formation and plantlet formation of the cells were equal to those of the unfrozen original cells. Cryostorage of cells in liquid nitrogen is discussed in terms of the preservation of various desired types of cells.     

Isolation and Identification of l-Menthyl-β-d-glucoside from Shubi

Quinoxalines derived from d-galactose with o-phenylenediamine (OPD) in acidic media under reflux were studied by using GLC and NMR measurements. Four quinoxaline derivatives were obtained from the reaction mixture, and were identical with those derived from d-glucose. The yields of 2-(D-lyxo-tetrahydroxybutyl)quinoxaline (GA-III), and the stereoisomeric derivative of GA-III, i.e., 2-(D-arabino-tetrahydroxybutyl)quinoxaline (ATBQ), were 13.2 and 5.3–, respectively. The ratio of GA-III to ATBQ derived from d-galactose was reciprocally coincident with that from d-glucose. Some proposals are made on the relationship between the isomerization of these sugars and the formation of quinoxaline derivatives.     

Studies on Lactic Acid Fermentation

Resting cells of l. fermentum convert glyceraldehyde to equimolar lactic acid and neither the evolution of carbon dioxide nor the uptake of oxygen was observed. Glyceraldehyde-3-phosphate and 3-phosphoglycerate were identified as intermediates which were equally labeled with inorganic P³² in reaction systems, and the presence of triokinase was suggested.