Mobility study of individual residue sites in the carbohydrate recognition domain of LSECtin using SDSL-EPR technique.

Conformational changes in proteins profoundly influence their functional profiles. With site-directed spin labeling (SDSL)-electron paramagnetic resonance (EPR) spectroscopy, we investigated the mobility features of individual residue sites in the carbohydrate recognition domain (CRD) of LSECtin, a type II integral membrane protein. The mobility of six different residue sites scatting around the Ca(2+)-1-binding site were investigated by comparing their EPR spectra rotational correlation time τ(c) in order to obtain the information of conformational changes of relevant region. The results showed that the overall mobility of LSECtin-CRD increased after addition of Ca(2+) and N-acetylglucosamine, but different sites in the CRD exhibited different mobility features, suggesting that these sites may have different functional profiles. The preliminary observations thus demonstrated that SDSL-EPR spectroscopy is not only an effective technique to reveal the mobility of single residue sites in LSECtin-CRD but also that the functions of single residue sites may be indicated by their conformational dynamics.