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Quick-freeze deep-etch of the P-face (Pcv) of the
contractile vacuole. This face has many IMPs that are presumably
transmembrane proteins many of which have been pulled free of the
leaflet illustrated in Fig. 41. There are also pits in this leaflet
which represent the IMPs that remain with the opposite leaflet.
Although we have found no mechano-sensitive or voltage-gated channels
in the CVC (Sugino et al., J. Exp. Biol. 208:3957-3969, 2005)) it is
clear that proton pumps are present in the decorated tubules and that
protons are exchanged for other ions such as calcium, potassium and
sodium as these ions can accumulate in the CV against a concentration
gradient from the cytosol. Some of the IMPs may function as ion
exchange channels. What caused the large holes is not known
(arrowheads). The texture of the luminal contents
(lucv) resembles the CV content and indicates the
membrane is indeed that of the contractile vacuole. EM taken on
5/27/92 by R. Allen with Zeiss 10A TEM. Neg. 31,500X. Bar = 0.2µm.
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