Calcium transporting ATPases in plant cells.
(1997)- Abstract
- Plant cells carry Ca2+ ATPases to maintain the low resting level of cytosolic Ca2+ (0.1-0.2 µM) found in all eukaryotes. Plant Ca2+ ATPases are mainly located in the plasma membrane, the endoplasmic reticulum and in the vacuolar membrane, and consequently large Ca2+ gradients are created across these membranes. The Ca2+ gradients are used by the cell to transmit information in a variety of physiological processes, such as in tip growth, cell division and stress responses. Ca2+ signals involve the co-ordinated action of Ca2+ channels and Ca2+ pumps. Upon Ca2+ influx via Ca2+ channels, cytosolic Ca2+ increases. The subsequent extrusion of Ca2+, by Ca2+ ATPases, ends the Ca2+ signal and restores the resting cytosolic Ca2+ level. During signal... (More)
- Plant cells carry Ca2+ ATPases to maintain the low resting level of cytosolic Ca2+ (0.1-0.2 µM) found in all eukaryotes. Plant Ca2+ ATPases are mainly located in the plasma membrane, the endoplasmic reticulum and in the vacuolar membrane, and consequently large Ca2+ gradients are created across these membranes. The Ca2+ gradients are used by the cell to transmit information in a variety of physiological processes, such as in tip growth, cell division and stress responses. Ca2+ signals involve the co-ordinated action of Ca2+ channels and Ca2+ pumps. Upon Ca2+ influx via Ca2+ channels, cytosolic Ca2+ increases. The subsequent extrusion of Ca2+, by Ca2+ ATPases, ends the Ca2+ signal and restores the resting cytosolic Ca2+ level. During signal transduction, Ca2+ ATPases may also function in evoking the specificity in Ca2+ signals, i.e. by affecting the oscillating pattern of the Ca2+ signal. To understand how the distribution and regulation of Ca2+ ATPases in the plant cell can relate to a role of Ca2+ ATPases in signal transduction, specific Ca2+ ATPases were studied using isolated plant membrane vesicles.
Plasma membrane Ca2+ ATPases in wheat and spinach were characterised by high affinities for Ca2+ (Km * 0.6 µM for the activated form), pH optima at 7.2-7.3 and low substrate specificities (30-50% activities with GTP and ITP in comparison to ATP). The plasma membrane Ca2+ ATPases in wheat and spinach were stimulated by calmodulin 2 to 4-fold. The stimulations were through an increase in Vmax as well as in the affinity for Ca2+, and involved a 11-kDa terminal fragment (spinach). Calmodulin binding to the 120-kDa spinach plasma membrane Ca2+ ATPase was strictly Ca2+ dependent. An endoplasmic reticulum Ca2+ ATPase in wheat was stimulated by calmodulin up to 5-fold, but differed from the plasma membrane Ca2+ ATPases in showing a lower pH optimum (pH 6.8) and a high specificity for ATP.
Differences in pH optima between Ca2+ ATPases in different subcellular membranes may have physiological significance since pH fluctuations may specify Ca2+ signals. Ca2+-calmodulin interaction with Ca2+ ATPases provides a feedback mechanism for regulation of cytosolic Ca2+ extrusion, which can agree with a role of Ca2+ ATPases in modulating Ca2+ oscillations. (Less)
Please use this url to cite or link to this publication:
https://lup.lub.lu.se/record/29711
- author
- Olbe, Malin LU
- supervisor
- opponent
-
- Prof De Michelis, I.M.
- organization
- publishing date
- 1997
- type
- Thesis
- publication status
- published
- subject
- keywords
- Triticum aestivum, calcium, Brij 58, calmodulin, Ca2+ signalling, inside-out, endoplasmic reticulum, plant, plasma membrane, proteolysis, P-type ATPase, spinach, Spinacea oleracea, trypsin, two-phase, wheat., Plant biochemistry, Växtbiokemi
- pages
- 131 pages
- publisher
- Department of Plant Biochemistry, Lund University
- defense location
- Department of Plant Biochemistry, Lund
- defense date
- 1997-12-12 10:15:00
- external identifiers
-
- other:ISRN: LUNKDL/NKVK-97/1011
- ISBN
- 91-973252-1-X
- language
- English
- LU publication?
- yes
- id
- dddd6d6f-3689-4309-984e-a563f96e3872 (old id 29711)
- date added to LUP
- 2016-04-04 11:19:28
- date last changed
- 2018-11-21 21:04:05
@phdthesis{dddd6d6f-3689-4309-984e-a563f96e3872,
abstract = {{Plant cells carry Ca2+ ATPases to maintain the low resting level of cytosolic Ca2+ (0.1-0.2 µM) found in all eukaryotes. Plant Ca2+ ATPases are mainly located in the plasma membrane, the endoplasmic reticulum and in the vacuolar membrane, and consequently large Ca2+ gradients are created across these membranes. The Ca2+ gradients are used by the cell to transmit information in a variety of physiological processes, such as in tip growth, cell division and stress responses. Ca2+ signals involve the co-ordinated action of Ca2+ channels and Ca2+ pumps. Upon Ca2+ influx via Ca2+ channels, cytosolic Ca2+ increases. The subsequent extrusion of Ca2+, by Ca2+ ATPases, ends the Ca2+ signal and restores the resting cytosolic Ca2+ level. During signal transduction, Ca2+ ATPases may also function in evoking the specificity in Ca2+ signals, i.e. by affecting the oscillating pattern of the Ca2+ signal. To understand how the distribution and regulation of Ca2+ ATPases in the plant cell can relate to a role of Ca2+ ATPases in signal transduction, specific Ca2+ ATPases were studied using isolated plant membrane vesicles.<br/><br>
<br/><br>
Plasma membrane Ca2+ ATPases in wheat and spinach were characterised by high affinities for Ca2+ (Km * 0.6 µM for the activated form), pH optima at 7.2-7.3 and low substrate specificities (30-50% activities with GTP and ITP in comparison to ATP). The plasma membrane Ca2+ ATPases in wheat and spinach were stimulated by calmodulin 2 to 4-fold. The stimulations were through an increase in Vmax as well as in the affinity for Ca2+, and involved a 11-kDa terminal fragment (spinach). Calmodulin binding to the 120-kDa spinach plasma membrane Ca2+ ATPase was strictly Ca2+ dependent. An endoplasmic reticulum Ca2+ ATPase in wheat was stimulated by calmodulin up to 5-fold, but differed from the plasma membrane Ca2+ ATPases in showing a lower pH optimum (pH 6.8) and a high specificity for ATP.<br/><br>
<br/><br>
Differences in pH optima between Ca2+ ATPases in different subcellular membranes may have physiological significance since pH fluctuations may specify Ca2+ signals. Ca2+-calmodulin interaction with Ca2+ ATPases provides a feedback mechanism for regulation of cytosolic Ca2+ extrusion, which can agree with a role of Ca2+ ATPases in modulating Ca2+ oscillations.}},
author = {{Olbe, Malin}},
isbn = {{91-973252-1-X}},
keywords = {{Triticum aestivum; calcium; Brij 58; calmodulin; Ca2+ signalling; inside-out; endoplasmic reticulum; plant; plasma membrane; proteolysis; P-type ATPase; spinach; Spinacea oleracea; trypsin; two-phase; wheat.; Plant biochemistry; Växtbiokemi}},
language = {{eng}},
publisher = {{Department of Plant Biochemistry, Lund University}},
school = {{Lund University}},
title = {{Calcium transporting ATPases in plant cells.}},
year = {{1997}},
}