Active Transport of l-Valine by Streptococcus Diacetilactis

Incorporation of radioactive acetate into diacetyl by Streptococcus diacetilactis.

Streptococcus diacetilactis was grown in a partially defined, lipoic acid-free medium containing radioactive acetate with and without addition of 0.1% unlabeled sodium pyruvate. Labeled carbon was incorporated into diacetyl, but neither the amount of diacetyl produced nor its specific activity was influenced by addition of pyruvate. Acetoin had low specific activity, indicating that it was a mi...

Transport of sugars and amino acids in bacteria. IV. Regulation of valine transport activity by valine and cysteine.

The properties of the carrier for isoleucine in Escherichia coli were studied using cytoplasmic membrane vesicles (IM vesicles) prepared by the method of Yamato, Anraku, and Hirosawa (J. Biochem. 77, 705 (1975)). The IM vesicles exhibited respiration-dependent isoleucine transport activity which was more than 30-fold higher than that of "Kaback vesicles" prepared by our hand from the same strai...

Uptake of L-valyl-L-valine and glycylsarcosine by hamster jejunum in vitro.

A non-planar peptide bond in L-seryl-L-valine.

The molecular structure of (I) is shown in Fig. 1. Bond lengths and angles are normal, but the unusual non-planarity of the peptide bond is quite evident. The associated torsion angle C1ÐC3ÐN2ÐC4 (!) is 157.37 (15) , a deviation from 180 that is superceded among small chiral peptides only by the 156.6 ! angle in N-(tert-butoxycarbonyl)-l-Pro-l-Leu benzyl ester (Sugino et al., 1978). Fig. 2(a) s...

Intracellular transport by active diffusion.

All substances exhibit constant random motion at the microscopic scale. This is a direct consequence of thermal agitation, and leads to diffusion of molecules and small particles in a liquid. In addition to this nondirected motion, living cells also use active transport mechanisms, such as motor activity and polymerization forces that depend on linear biopolymers and are therefore fundamentally...