Abstract
Bicarbonate depletion of chloroplast thylakoids reduces the affinity of the herbicide, ioxynil, to its binding site in Photosystem (PS) II. This herbicide is found to be a relatively more efficient inhibitor of the Hill reaction when HCO- 3 is added to CO2-depleted thylakoids in subsaturating rather than in saturating concentrations. The reason for this dependence of the inhibitor efficiency on the HCO- 3 concentration is that the inactive HCO- 3-deficient PS II reaction chains bind less ioxynil than the active PS II electron-transport chains that have bound HCO- 3, and, thus, after addition of a certain amount of ioxynil the concentration of the free herbicide increases when the HCO- 3 concentration decreases. Therefore, the inhibition of electron transport by ioxynil increases at decreasing HCO- 3 levels. Measurements on the effects of modification of lysine and arginine residues on the rate of electron transport are also presented: the rate of modification is faster in the presence than in the absence of HCO- 3. Therefore, we suggest that surface-exposed lysine or arginine residues are not involved in binding of HCO- 3 (or CO2 or CO2- 3) to its binding protein, but that HCO- 3 influences the conformation of its binding environment such that the affinity for certain herbicides and the accessibility for amino acid modifiers are changed.
| Original language | English (US) |
|---|---|
| Pages (from-to) | 242-247 |
| Number of pages | 6 |
| Journal | BBA - Bioenergetics |
| Volume | 681 |
| Issue number | 2 |
| DOIs | |
| State | Published - Aug 20 1982 |
| Externally published | Yes |
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Keywords
- (Pea chloroplast)
- Bicarbonate effect
- Herbicide
- Photosystem II
- Protein modification
- Thylakoid membrane
ASJC Scopus subject areas
- Biophysics
- Medicine(all)
Cite this
The interaction between bicarbonate and the herbicide ioxynil in the thylakoid membrane and the effects of amino acid modification on bicarbonate action. / Vermaas, Willem; Van Rensen, Jack J S; Govindjee.
In: BBA - Bioenergetics, Vol. 681, No. 2, 20.08.1982, p. 242-247.Research output: Contribution to journal › Article
}
TY - JOUR
T1 - The interaction between bicarbonate and the herbicide ioxynil in the thylakoid membrane and the effects of amino acid modification on bicarbonate action
AU - Vermaas, Willem
AU - Van Rensen, Jack J S
AU - Govindjee,
PY - 1982/8/20
Y1 - 1982/8/20
N2 - Bicarbonate depletion of chloroplast thylakoids reduces the affinity of the herbicide, ioxynil, to its binding site in Photosystem (PS) II. This herbicide is found to be a relatively more efficient inhibitor of the Hill reaction when HCO- 3 is added to CO2-depleted thylakoids in subsaturating rather than in saturating concentrations. The reason for this dependence of the inhibitor efficiency on the HCO- 3 concentration is that the inactive HCO- 3-deficient PS II reaction chains bind less ioxynil than the active PS II electron-transport chains that have bound HCO- 3, and, thus, after addition of a certain amount of ioxynil the concentration of the free herbicide increases when the HCO- 3 concentration decreases. Therefore, the inhibition of electron transport by ioxynil increases at decreasing HCO- 3 levels. Measurements on the effects of modification of lysine and arginine residues on the rate of electron transport are also presented: the rate of modification is faster in the presence than in the absence of HCO- 3. Therefore, we suggest that surface-exposed lysine or arginine residues are not involved in binding of HCO- 3 (or CO2 or CO2- 3) to its binding protein, but that HCO- 3 influences the conformation of its binding environment such that the affinity for certain herbicides and the accessibility for amino acid modifiers are changed.
AB - Bicarbonate depletion of chloroplast thylakoids reduces the affinity of the herbicide, ioxynil, to its binding site in Photosystem (PS) II. This herbicide is found to be a relatively more efficient inhibitor of the Hill reaction when HCO- 3 is added to CO2-depleted thylakoids in subsaturating rather than in saturating concentrations. The reason for this dependence of the inhibitor efficiency on the HCO- 3 concentration is that the inactive HCO- 3-deficient PS II reaction chains bind less ioxynil than the active PS II electron-transport chains that have bound HCO- 3, and, thus, after addition of a certain amount of ioxynil the concentration of the free herbicide increases when the HCO- 3 concentration decreases. Therefore, the inhibition of electron transport by ioxynil increases at decreasing HCO- 3 levels. Measurements on the effects of modification of lysine and arginine residues on the rate of electron transport are also presented: the rate of modification is faster in the presence than in the absence of HCO- 3. Therefore, we suggest that surface-exposed lysine or arginine residues are not involved in binding of HCO- 3 (or CO2 or CO2- 3) to its binding protein, but that HCO- 3 influences the conformation of its binding environment such that the affinity for certain herbicides and the accessibility for amino acid modifiers are changed.
KW - (Pea chloroplast)
KW - Bicarbonate effect
KW - Herbicide
KW - Photosystem II
KW - Protein modification
KW - Thylakoid membrane
UR - http://www.scopus.com/inward/record.url?scp=0020399310&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=0020399310&partnerID=8YFLogxK
U2 - 10.1016/0005-2728(82)90028-7
DO - 10.1016/0005-2728(82)90028-7
M3 - Article
VL - 681
SP - 242
EP - 247
JO - Biochimica et Biophysica Acta - Bioenergetics
JF - Biochimica et Biophysica Acta - Bioenergetics
SN - 0005-2728
IS - 2
ER -