H+ -mediated coupling of transmembrane Ca2+ fluxes in vegetative Trichoderma viride mycelia suggested by the study of ageing and adaptation to extreme Ca2+ concentrations.
The adaptation to extreme concentrations of Ca(2+) and its consequence on the properties of the (45)Ca(2+) transport were studied in submerged mycelia of Trichoderma viride. The adaptation to low [Ca(2+)](o) did not cause changes in kinetic parameters of the (45)Ca(2+) influx but the adaptation to high [Ca(2+)](o) increased the K(M(Ca2+)). The V(max) of the (45)Ca(2+) influx decreased with the age of (non-adapted) mycelia with concomitant decrease of the K(M(Ca2+)) these changes were prevented in mycelia adapted to high Ca(2+). High [Ca(2+)](o) decreased the stimulation by the uncoupler, 3, 3', 4', 5-tetrachloro salicylanilide (TCS) (30 muM), as compared to the control, whereas the Ca(2+) chelator, EGTA, stimulated it. In the aged mycelia, the stimulation by TCS of the (45)Ca(2+) influx faded away, in parallel with the activity of the H(+)-ATPase. The (45)Ca(2+) efflux from mycelia was affected by TCS in a similar way as the (45)Ca(2+) influx. The results demonstrate the adaptive responses of transport processes participating in the mycelial Ca(2+) homeostasis and ageing are in agreement with a notion that both Ca(2+)-influx and-efflux are coupled by the H(+)-homeostasis at the plasma membrane.
Ditte
Peter
P
Department of Biochemistry and Microbiology, Faculty of Chemical and Food Technology, Slovak University of Technology, Radlinského 9, 81237-Bratislava, Slovakia.
Lakatos
Boris
B
Varecka
L'udovít
L
Simkovic
Martin
M
D002118:Calcium / Q000378:metabolism*; D002462:Cell Membrane / Q000201:enzymology / Q000378:metabolism; D017136:Ion Transport; D006180:Proton-Translocating ATPases / Q000378:metabolism; D011522:Protons; D014242:Trichoderma / Q000378:metabolism*
D011522:Protons; D006180:Proton-Translocating ATPases; D002118:Calcium