scholarly journals Sterol structural requirements for inhibition of streptolysin O activity

1974 ◽  
Vol 140 (1) ◽  
pp. 95-98 ◽  
Author(s):  
Kenneth C. Watson ◽  
Eric J. C. Kerr
Keyword(s):  
Cell Membranes ◽  
Human Erythrocytes ◽  
Hydroxyl Group ◽  
Membrane Cholesterol ◽  
Specific Requirement ◽  
Structural Requirements ◽  
Hydrophilic Group ◽  
Streptolysin O

Reduced streptolysin O, a toxin produced by certain β-haemolytic streptococci, lyses human erythrocytes. The reaction is inhibited by cholesterol at concentrations of about 1.0μg/ml. Other sterols inhibit the lysin and there is a specific requirement for a 3β-hydroxyl group. Inhibition was obtained with 3β-hydroxychol-5-en-24-oic acid, containing a hydrophilic group at C-24. The mode of inhibition is likely to involve attachment to the fixation site of the lysin which attaches the molecule to cell membranes, probably to membrane cholesterol. A second streptolysin site, concerned in the final haemolytic event, may also be involved. Inhibitors of the latter site have not been characterized, other than antibody with specificity for the site.

Stimulation of 24R,25-dihydroxyvitamin D3 synthesis by metabolites of vitamin D3

1983 ◽  
Vol 245 (4) ◽  
pp. E359-E364 ◽  
Author(s):  
G. S. Reddy ◽  
G. Jones ◽  
S. W. Kooh ◽  
D. Fraser ◽  
H. F. DeLuca
Keyword(s):  
Vitamin D ◽  
Vitamin D3 ◽  
The Other ◽  
Hydroxyl Group ◽  
Vitamin D Metabolites ◽  
Structural Requirements ◽  
Dihydroxyvitamin D3 ◽  
Hydroxylated Metabolites ◽  
Perfusion Period ◽  
Stimulation Of

Previously we have shown that the isolated perfused kidney from vitamin D-deficient rats converts [3H]25(OH)D3 into [3H]1 alpha,25(OH)2D3. When certain vitamin D metabolites were added to perfusate the same kidney began to synthesize [3H]24R,25(OH)2D3. In this study we investigated the structural requirements of the vitamin D molecule necessary to stimulate synthesis of [3H]24R,25(OH)2D3 in a 1-hydroxylating kidney. Kidneys were perfused with tracer [3H]25(OH)D3 (450 pM) alone and in the presence of a variety of hydroxylated metabolites and fluorinated analogues of vitamin D3 at concentrations of 450 pM to 25 microM. Tracer [3H]25(OH)D3 alone resulted in synthesis of only [3H]1 alpha,25(OH)2D3 during the 6-h perfusion period. 25-Hydroxylated metabolites [25(OH)D3, 25 nM; 1 alpha,25(OH)2D3, 25 nM; 24R,25(OH)2D3, 25 nM; 24(F)2,25(OH)D3, 50 nM] stimulated [3H]24R,25(OH)2D3 production at 2 h of perfusion. On the other hand, analogues without the 25-hydroxyl group [D3; 1 alpha(OH)D3; 25(F)D3; 1 alpha(OH),25(F)D3; 1 alpha(F)D3; 1 beta(F)D3]; did not stimulate [3H]24R,25(OH)2D3 synthesis. We conclude that the 25-hydroxyl group is an essential determinant of 24-hydroxylation.

Activation by hemoglobin of the Ca2+-requiring neutral proteinase of human erythrocytes: Structural requirements

1984 ◽  
Vol 123 (1) ◽  
pp. 331-337 ◽  
Author(s):  
S. Pontremoli ◽  
B. Sparatore ◽  
E. Melloni ◽  
M. Michetti ◽  
B.L. Horecker
Keyword(s):  
Human Erythrocytes ◽  
Structural Requirements ◽  
Neutral Proteinase

scholarly journals ANTIGEN RECOGNITION AND THE IMMUNE RESPONSE

1972 ◽  
Vol 136 (2) ◽  
pp. 387-391 ◽  
Author(s):  
Sefik S. Alkan ◽  
Maurice E. Bush ◽  
Danute E. Nitecki ◽  
Joel W. Goodman
Keyword(s):  
Immune Response ◽  
Hydroxyl Group ◽  
Side Chain ◽  
Low Molecular Weight ◽  
Carboxyl Group ◽  
Amino Group ◽  
Structural Requirements ◽  
Phenolic Ring ◽  
Cellular Immune ◽  
Charged Group

The low molecular weight compound L-tyrosine-azobenzenearsonate (RAT) induces a cellular immune response in guinea pigs. The contribution of the side chain of tyrosine to the immunogenicity of RAT and the structural requirements at that position for immunogenicity were assessed by synthesizing a series of analogs of RAT containing modifications in the side chain of tyrosine and employing them as immunogens. Removal of either the carboxyl or amino group did not markedly affect immunogenicity, measured by the induction of delayed cutaneous sensitivity, whereas deletion of both completely abolished it. However, a charged group was not required since side chains containing a polar hydroxyl group could substitute for chains bearing an amino or carboxyl group. The size of the side chain exerted a pronounced influence; the charged or polar substituent had to be extended from the phenolic ring by at least two carbon atoms in order to confer immunogenicity.

scholarly journals Structural requirements for active intestinal transport. The nature of the carrier–sugar bonding at C-2 and the ring oxygen of the sugar

1970 ◽  
Vol 118 (5) ◽  
pp. 843-850 ◽  
Author(s):  
J. E. G. Barnett ◽  
A. Ralph ◽  
K. A. Munday
Keyword(s):  
Oxygen Atom ◽  
Intestinal Transport ◽  
Competitive Inhibitor ◽  
Hydroxyl Group ◽  
Hydroxyl Groups ◽  
Sulphur Atom ◽  
Intestinal Tissue ◽  
Structural Requirements ◽  
Galactose Transport ◽  
Steric Constraints

Several weakly transported sugars were tested for transport by the Na+-dependent sugar carrier with slices of everted hamster intestinal tissue. Sugars were assumed to be transported by this carrier if the accumulation was diminished in the absence of Na+ and in the presence of the competitive inhibitor 1,5-anhydro-d-glucitol. The extent of accumulation was correlated with the number of hydroxyl groups in the d-gluco configuration if the ring oxygen was placed in the normal d-glucose position. 5-Thio-d-glucose, with a sulphur atom in the ring, was transported at about the same rate as d-glucose and had a similar Ki for d-galactose transport, but myoinositol was poorly accumulated. It is suggested that there is no hydrogen bonding at the ring oxygen atom, but that the oxygen atom is found at this position as a result of steric constraints. No sugar without a hydroxyl group in the d-gluco position at C-2 of the sugar, including d-mannose, 2-deoxy-d-glucose, 2-chloro-2-deoxy-d-glucose and 2-deoxy-2-fluoro-d-glucose, was transported by the Na+-dependent carrier, but these sugars and l-fucose weakly and competitively inhibit the Na+-dependent accumulation of l-glucose into slices of everted hamster intestinal tissue. It is concluded that the bond between the carrier and C-2 of the sugar may be covalent, and a possible mechanism for active intestinal transport is proposed.

Effects of AlCl3 on toad skin, human erythrocytes, and model cell membranes

2001 ◽  
Vol 55 (2) ◽  
pp. 205-210 ◽  
Author(s):  
M Suwalsky ◽  
B Ungerer ◽  
F Villena ◽  
B Norris ◽  
H Cárdenas ◽  
...  
Keyword(s):  
Cell Membranes ◽  
Human Erythrocytes ◽  
Toad Skin ◽  
Model Cell

CO 2 permeability of cell membranes is regulated by membrane cholesterol and protein gas channels

2012 ◽  
Vol 26 (12) ◽  
pp. 5182-5191 ◽  
Author(s):  
Fabian Itel ◽  
Samer Al‐Samir ◽  
Fredrik Öberg ◽  
Mohamed Chami ◽  
Manish Kumar ◽  
...  
Keyword(s):  
Cell Membranes ◽  
Membrane Cholesterol
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