Abstract
Plant non-specific lipid transfer proteins (nsLTPs) are small and basic proteins. They are mainly divided into two subfamilies according to their molecular masses: nsLTP1 (9-kDa) and nsLTP2 (7-kDa). Recently, some anther-specific proteins have considerable homologies with plant nsLTPs, and have been classified as nsLTP3. However, the lipid transfer ability and biophysical properties of nsLTP3 is still unclear. In this study we focused on a nsLTP2 (Os01g49650, abbreviation LTP49) and a nsLTP3 (Os08g43290, abbreviation LTP43), which were reported to be involved in anther male sterility. They both exhibited highly structural stabilities against temperature (up to96℃) from the results of circular dichroism (CD) spectroscopy. In chemical denaturation experiments, a higher concentration of GdnHCl was required to denature LTP3 (Cm > 6M) than the concentration of LTP49 (Cm ~3.2M). Furthermore, the functional assays of lipid binding and lipid transfer activities were performed. The results showed that LTP49 displayed both lipid binding and lipid transfer activities while LTP43 could not interact with lipid molecules. We proposed that the hydrophobic cavity of LTP43 might be small or buried in the structure from the fluorescence data. Besides, the docking model was constructed to mimic the LTP49-lipid complex structure and all the results suggested that some lipids could bind into the hydrophobic cavity of LTP49. In the near future, several 2D and 3D NMR spectra has been carried out and the solution structures of these two nsLTP would be determined to further figure out the relationships between structure and binding/transfer activity of nsLTPs.