Protein domains required for formation of stable monomeric Lhca1- and Lhca4-complexes |
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Authors: | Rupprecht Jens Paulsen Harald Schmid Volkmar HR |
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Institution: | 1.Institut für Allgemeine Botanik, Johannes Gutenberg-Universit?t, Müllerweg 6, 55099, Mainz, Germany ; |
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Abstract: | The peripheral light-harvesting complex of Photosystem I consists of two subpopulations, LHC I-680 and LHC I-730. The latter
is composed of the two apoproteins Lhca1 and Lhca4. Recently, reconstitution of monomeric LHC I using bacterially overexpressed
Lhca1 or Lhca4 was achieved. In order to obtain insight into the structure requirements for formation of monomeric light-harvesting
complexes, we produced a series of N- and C-terminal deletion mutants and used the overexpressed proteins for reconstitution
experiments. We found the entire extrinsic N-terminal region dispensable for monomer formation in Lhca1 and Lhca4. Also at
the C-terminus, both subunits revealed similarity since all amino acids up to the end of the fourth helix could be removed
without abolishing monomer formation. In connection with former corresponding results for Lhcb1, the dispensability of these
regions appears to be a general feature in LHC-formation. In LHC I, however, a stabilising effect can be ascribed to these
regions since the yield of complexes was decreased. In the majority of the mutant LHC I versions no effect on pigment binding
was detected. However, in the LHC with the most extensively N-terminally truncated mutant of Lhca4 a dramatic shift in the
77 K fluorescence emission to shorter wavelengths was observed. This suggests that chlorophylls involved in long wavelength
fluorescence emission are located in the chlorophyll array located towards the stromal face of the thylakoid membrane assuming
a pigment arrangement corresponding to that in LHC II and CP29.
This revised version was published online in June 2006 with corrections to the Cover Date. |
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Keywords: | antenna Lhca1 Lhca4 LHC I-730 light-harvesting complexes pigment– protein complex Photosystem I Photosynthesis protein structure reconstitution |
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