Şen, MehmetLe, TrevorManandhar, Pragya2018-02-272018-02-272017-10-12http://hdl.handle.net/10657/2510αXβ2 integrin is central to the migration of myeloid cells during inflammatory response. The ligand binding domain of αXβ2, called αX I-domain, has a Mg2+-binding site (MIDAS) and an allosteric α7-helix. It has been postulated that the MIDAS site crosstalks with α7-helix and this cross-talk is associated with conformational change within the fold of the αX I-domain, yet biochemical basis of this cross-talk has yet to be elucidated. Our hypothesis is that MIDAS/α7-helix crosstalk exists in a thermodynamic equilibrium between ensembles of open and closed states. Our goal is to test how the observed conformational changes alters Mg2+-affinity to MIDAS as well as the thermal stability of the αX I-domain in solution. Conclusions. Mg2+ affinity to the intact αX-I domain is 4.848 mM ± 0.133 (Fig.X1) and the αX I-domain locked in an open-alternate conformation by I314G mutation on the αI α7-helix is 1.006 mM ± 0.050 (Fig.X2). However, the high range of melting temperature in the I314G αX I-domain suggests that the transition could potentially be bi-phasic involving two different binding-phases with the dissociation constants of 0.146 mM ± 0.020 and 3.328 mM ± 0.325. This observation is an indication that a multiple ensemble of conformations could exist between the open and closed states of the αX I-domain. These observations indicate that 1) Mg2+ stabilizes the αX-I domain and 2) smaller range of melting (40-48 ºC) of the intact αX I-domain compared to that of I314G αX I-domain (43-55 ºC) shows that the close state is less dynamic than the open state.en-USThe author of this work is the copyright owner. UH Libraries and the Texas Digital Library have their permission to store and provide access to this work. Further transmission, reproduction, or presentation of this work is prohibited except with permission of the author(s).Poster