| Summary: | 博士 === 國立清華大學 === 生物資訊與結構生物研究所 === 102 === Leptospirosis is one of the most widespread zoonotic diseases in the world. It is caused by the pathogen Leptospira that results in multiple-organ failure, in particular of the kidney. Outer membrane lipoprotein is the suspected virulence factor of Leptospira. In Leptospira spp LipL41 is one major lipoprotein and is highly conserved. Previous study suggests that LipL41 bears hemin-binding ability and might play a possible role in iron regulation and storage. However, the characterization of hemin-binding ability of LipL41 is still unclear. Here the hemin-binding ability of LipL41 was examined, yielding a Kd = 0.59 ± 0.14 μM. Two possible heme regulatory motifs (HRMs), C[P/S], were found in LipL41 at 140Cys-Ser and 220Cys-Pro. The mutational study indicates that Cys140 and Cys220 might be cooperatively involved in hemin binding. A supramolecular assembly of LipL41 was determined by transmission electron microscopy. The LipL41 oligomer consists of 36 molecules and folds as a double-layered yo-yo particle. At the C-terminus of LipL41, there are two tetratricopeptide repeats (TPRs), which might be involved in the protein-protein interaction of the supramolecular assembly. Besides, the TPR-containing fragment, LipL41-C100, shows thermal stability and reversibility by circular dichroism and NMR. The flexible folding of LipL41-C100 can be stabilized by adding 50% TFE. The thermal dynamics and flexible folding consider that LipL41-C100 is a molten globule protein, which conserves a native-like secondary structure content but without the tightly packed protein interior.
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