Attempts at purifying the galactose carrier from galactose-induced baker's yeast

Glucose induces two amino acid transport systems in Chlorella

In autotrophically grown Chlorella cells, glucose induces a hexose transport system but, at the same time, the synthesis of two amino acid transport systems is also induced. Thus, the rates of uptake of glycine, L-alanine, L-proline, and L-serine, all of which compete with each other for entry into the cells, increase more than 100-fold when the algae are pretreated with glucose. The rates of L-arginine and L-lysine uptake increase by a factor of 25 to 50. The accumulation of proline and arginine within the cells amounts to 200- and 600-fold, respectively. Glucose does not cause the positive effect on amino acid uptake by serving as metabolic substrate because the nonmetabolizable 6-deoxyglucose also acts as inducer. Cycloheximide prevents the induction. The induced transport system for the four neutral amino acids has a turnover with a half-life of 7 hr, which corresponds closely to the half-life of the hexose transport system. The transport system for the basic amino acids, on the other hand, disappears with a half-life of 25 hr.

Loss of inducible D-galactose transport by baker's yeast after osmotic treatment

The ability of Saccharomyces cerevisiae to transport D-galactose and related sugars with an axial hydroxyl group at C-4, acquired by induction with D-galactose, was lost either by exposing early exponential-phase cells to an osmotic shock involving incubation in 0.6M NaC1O4, 0.66M sucrose and 1mM histidine and transfer to 5mM Tris-HC1 with 2mM dithiothreitol, or simply by transferring them to distilled water. The total amount of protein thus released was 0.1--0.35 and 0.1 mg per mg dry wt., respectively. The shock fluid contained at least six proteins, among them a galactose-binding component. L-Arabinose transport could not be restored by adding the concentrated shock fluid to depleted cells but cells remained viable after the shock and resynthesized the transport system if incubated in a galactose-containing growth medium.

Isolation and properties of an arginine-binding protein from Saccharomyces cerevisiae

Transfer of exponentially growing cells of Saccharomyces cerevisiae epsilon 1278 b to a fresh medium (or simply to distilled water) resulted in the loss of ability to transport arginine (and lysine), accompanied by the release of several proteins from the membrane surface or periplasmic space. Fractionation by ultrafiltration, Sephadex G-50 chromatography and freeze-drying yielded a homogeneous protein (55 mg per 100 g dry weight of cells) with specific binding ability for L-arginine (Kd = 3.8 X 10(-1) M) and L-lysine (Ki = 4.2 X 10(-4) M). The protein contains over 40 amino acid residues and has a molecular weight of about 5,000. In solution, it appears to aggregate as its concentration is raised, thereby decreasing the overall binding capacity for arginine. Addition of the protein to a depleted culture does not restore the transport of arginine. It is apparently the recognition protein for the specific arginine-transporting system of Saccharomyces cerevisiae but it occurs in almost identical amounts in the MG 168 mutant with impaired arginine transport.