The Structure And Function Of Fucoxanthin-Chlorophyll A/c Protein Complex From Phaeodactylum Tricornutum Diatom

In this study, we optimized the isolation method of fucoxanthin-chlorophyll protein (FCP) from Phaeodactylum tricornutum. Amino acids sequence, pigments and properties of spectra were analyzed after getting FCP proteins in high purity and homogeneity. Amino acids sequence analysis showed FCP was constituted by 198 amino acids which had sequence an identity of 24 percent comparing to that higher plant of LHCII. Molecular structuresimulation indicated this FCP had three short transmembrane helixes like that in LHCII without helix on membrane surface. Chlorophyll a, chlorophyll c and fucoxanthin were bound in FCP with a chl a/c ratio at 3.0. Absorption and fluorescence spectra proved fucoxanthin is able to absorb and transfer green light energy to chlorophyll in high efficiency to increase absorb enough energy when living under water with low light. Moreover, the light energy absorbed by fucoxanthin at 400-500 nm was transferred in low efficiency, playing a role of photoprotect under strong light. The binding sites for 4 chlorophylls were suggested by the conserved amino acids analysis, but fucoxanthin sites are difficult to be confirmed for its great flexibility. We get the crystals by screening MbClass Ⅱ kit. We are optimizing the condition to get more regular and bigger crystals. The FCP crystal has been diffracte to a resolution of 2.9 A.