Biology Reference
In-Depth Information
O
O
H2
H
H2
O
P
OC
CC
O
P
O
OH
O
-
O
-
pKa 2.1
pKa 2.1
FIGURE 5.18
CL
e
Cardiolipin (Diphosphatidylglycerol).
CL (
Figure 5.18
) is the most unusual of the 7 common mammalian phospholipids. It is
essentially 2 PAs glued together by a glycerol. It has an oversized head containing 2 negative
charges due to the 2 dissociated phosphates and 4 acyl chains (
Figure 5.19
). CL has 3 potential
optically active carbons, one on each of the two
-2 phosphatidyl groups and the third on the
central carbon of the linking glycerol. Saturated chain CLs form normal lamellar phase (the
structure is can-shaped) while the more biologically relevant CLs containing highly unsatu-
rated chains prefer non-lamellar phases (the structure is a truncated pyramid with a wider
base than head). Under biological conditions where CL is dispersed with other phospho-
lipids (primarily PCs and PEs) the mixture prefers the lamellar (normal bilayer) phase.
Non-lamellar phases are discussed in Chapter 10.
CL is found primarily in the mitochondrial inner membrane where it constitutes about
20% of the total lipid and is closely linked with electron transport and oxidative phosphor-
ylation
[24]
. Particularly effective in supporting the bioenergetic processes are mitochondrial
CL with a high content of linoleic acid (18:2
6
9,12
). CL aggregates and stabilizes important
electron transport protein complexes including cytochrome c oxidase, NADH dehydroge-
nase, ATP synthase and various mitochondrial carrier proteins. While most lipids are
made in the endoplasmic reticulum, CL is synthesized on the matrix side of the inner mito-
chondrial membrane.
sn
_
_
FIGURE 5.19
Cartoon depiction of the structure of cardiolipin (CL).
