Investigation of the Conformational States of Wzz and the Wzz·O-Antigen Complex under Near-Physiological Conditions

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• 作者：Kuo-Hsiang Tang ; Hongjie Guo ; Wen Yi ; Ming-Daw Tsai ; Peng George Wang
• 刊名：Biochemistry
• 出版年：2007
• 出版时间：October 23, 2007
• 年：2007
• 卷：46
• 期：42
• 页码：11744 - 11752
• 全文大小：236K
• 年卷期：v.46,no.42(October 23, 2007)
• ISSN：1520-4995

文摘

Chain length determinant protein (Wzz) has been postulated to terminate the polymerizationand regulate the chain length of the O-polysaccharide (O-antigen), an important component for constructinglipopolysaccharide (LPS) in the outer membrane of Gram-negative bacteria. The investigation to understandthe mechanism of Wzz has been largely slowed down due to lack of structural information. In this report,we have applied small-angle X-ray scattering (SAXS) to study the conformational state and molecularproperties of Wzz and the Wzz·O-antigen complex under near-physiological conditions. No concentration-dependent aggregation or structural changes, but repulsive intermolecular interactions between Wzzmolecules, are suggested in the concentration series studies. The SAXS studies suggest that Wzz proteinappears to be elongated and exists as a tetramer in solution. The reconstructed model built from SAXSdata indicates that the middle regime of Wzz, most likely representing the periplasmic domain, contributesto the Wzz oligomerization, which has been proposed to be correlated to the function of Wzz. Theimmunoblotting analyses also demonstrate that the putative coiled-coil region in the periplasmic regioncontributes to the oligomerization. Further, the SAXS data corresponding to Wzz and the Wzz·O-antigencomplex indicate an apparent substrate (O-antigen)-induced conformational change, consistent with previouscircular dichroism studies. Our finding may shed light on the biological mechanism of Wzz as a chainlength determinant of O-antigen.