Employing discontinuous sucrose density gradient centrifugation of
n
-dodecyl β-d-maltoside-solubilized thylakoid membranes, three chlorophyll (Chl)-protein complexes containing Chl
a
, Chl
c
2
and peridinin in different proportions, were isolated from the dinoflagellates
Symbiodinium microadriaticum, S. kawagutii, S. pilosum
and
Heterocapsa pygmaea
. In
S. microadriaticum
, the first complex, containing 13% of the total cellular Chl
a
, and minor quantities of Chl
c
2
and peridinin, is associated with polypeptides with apparent molecular mass (
M
r
) of 8-9 kDa, and demonstrated inefficient energy transfer from the accessory pigments to Chl
a
. The second complex contains Chl
a
, Chl
c
2
and peridinin in a molar ratio of 1:1:2, associated with two apoproteins of
M
r
19-20 kDa, and comprises 45%, 75% and 70%, respectively, of the cellular Chl
a
, Chl
c
2
and peridinin. The efficient energy transfer from Chl
c
2
and peridinin to Chl
a
in this complex is supportive of a light-harvesting function. This Chl
a
-
c
2
- peridin-protein complex represents the major light-harvesting complex in dinoflagellates. The third complex obtained contains 12% of the cellular Chl
a
, and appears to be the core of photosystem I, associated with a light-harvesting complex. This complex is spectroscopically similar to analogous preparations from different taxonomic groups, but demonstrates a unique apoprotein composition. Antibodies against the water-soluble peridinin-Chl
a
-protein (sPCP) light-harvesting complexes failed to cross-react with any of the thylakoid-associated complexes, as did antibodies against Chl
a
-
c
-fucoxanthin apoprotein (from diatoms). Antibodies against the P
700
apoprotein of plants did not cross-react with the photosystem I complex. Similar results were observed in the other dinoflagellates.
Reconstitution of chlorophyll a/b light-harvesting complexes: Xanthophyll-dependent assembly and energy transfer
