Advanced

Calcium transporting ATPases in plant cells.

Olbe, Malin LU (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:
author
opponent
  • Prof De Michelis, I.M.
organization
publishing date
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
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
2007-06-13 11:44:24
date last changed
2016-09-19 08:45:09
@misc{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},
  keyword      = {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},
  pages        = {131},
  publisher    = {ARRAY(0x8f6b0c8)},
  title        = {Calcium transporting ATPases in plant cells.},
  year         = {1997},
}