The Structure And Function Study Of Human α1-microglobulin

Background The Lipocalins, found in animals, plants, and bacteria, is aprotein superfamily with30–35members. The protein family has a wellconserved three-dimensional structure, but exert surprisingly wide array ofbiological functions. As a member of the lipocalins, α1m, is a26-kDawidespread plasma and tissue glycoprotein. The high conservation inheredity among species and widespread in tissues indicate that α1m play animportant role in physiological activities, whereas, the research about thephysiological activity about α1m has not been reported by now. Resently,some researches report that α1m could degrade heme with the help of Hb,serving as a radical scavenger, exerts reductase and antioxidant properties.Nonetheless, little information is available about the α1m active sites (orregions) at which are involved in these functions.Objectives To resolve the three-dimensional structure of α1m, then tofurther investigate the biochemical and physiological function of the α1mbased on the structural information. Determination of the three-dimensionalstructure of α1m will help to understand how the human widespreadprotein exerts its multitudinous functions and help to develop theantioxidant and anti-inflammatory as well as immunoregulatory drugs. Methods Obtained the human α1M protein of enouph purity by cloning,expression, and purification, then determined its three-dimensionalstructure by crystallization and preliminary X-ray crystallographic studies;based on the three-dimensional structure, the function mechanism ofhuman α1M protein was analyzed by site-directed mutagenesis andspectroscopy method.Results The human α1M protein with95%purity was acquiredsuccessfully by cloning, expression and purification; the result of the sizeexclusion chromatography indicated that α1M protein exhibited as bothmonomer and dimer in the solution. We successfully obtained some goodsingle crystals that suitable to X-ray diffraction by protein crystal’sscreening and optimization, then we collected the diffraction data with theresolution was2.0and single-wavelength anomalous dispersion data withthe resolution was3.0; the three-dimensional structure of human α1Mprotein was successfully resolved. Additionally, the recombinant proteinexerted anti-oxidant activity by ABTS method.