Antimycobacterial activity of lipodepsipeptides produced by Pseudomonas syringae pv syringae B359.

Some lipodepsipeptides produced by Pseudomonas syringae pv. syringae showed strong antimycobacterial activity towards Mycobacterium smegmatis. MIC values found were between 1.

Epimerization of the D-valine portion in the biosynthesis of actinomycin D.

In the biosynthesis of actinomycin, the multifunctional actinomycin synthetase II (ACMS II) assembles 4-methyl-3-hydroxyanthranilic acid (4-MHA), L-threonine and D-valine, the first three residues of the 4-MHA peptide lactone chain. ACMS II activates L-threonine and L-valine but not D-valine as thioesters via their adenylates, and there is no epimerization of the covalently bound L-valine. When L-threonine and L-valine are presented to the enzyme together with the 4-MHA analogue p-toluic acid and the 4-MHA-activating enzyme ACMS I, ACMS II forms the two diastereomers p-toluyl-L-Thr-L-Val and p-toluyl-L-Thr-D-Val in equal amounts along with p-toluyl-L-Thr in a cofactor-independent manner.

Sodium dodecyl sulfate-polyacrylamide gel electrophoresis for M(r) estimations of high-molecular-weight polypeptides.

A convenient method was established for the M(r) estimation by sodium dodecyl sulfate-polyacrylamide gel electrophoresis of large polypeptides in the range from 250,000 to 600,000. Such polypeptides had previously been shown to migrate improperly in various gel electrophoresis systems. In a conventional Laemmli system with 3% polyacrylamide, approximately linear log M(r) vs Rf plots could be obtained by varying the gel thickness which ranged from 0.

The initiation of peptide formation in the biosynthesis of actinomycin.

Actinomycin Synthetase II (ACMS II), which activates threonine and valine by a thioltemplate mechanism during the synthesis of the actinomycin half-molecule 4-methyl-3-hydroxyanthranilic acid (4-MHA) pentapeptide lactone, was purified to near homogeneity from Streptomyces chrysomallus. It is a single polypeptide chain of M(r) 280,000 and contains 4'-phosphopantetheine as a covalently bound prosthetic group. ACMS II charges itself with threonine but not with the 4-MHA analogue p-toluic acid via a specific sulfhydryl group at the expense of ATP.