Non-symbiotic hemoglobin conformational space dependence on the heme coordination using nESI-TIMS-TOF MS

作者：Butcher David; Bernad Sophie; Derrien Valerie; Sebban Pierre; Miksovska Jaroslava; Fernandez Lima Francisco^*

来源：International Journal of Mass Spectrometry, 2018, 430(3): 37-43.

DOI：10.1016/j.ijms.2018.03.008

• Trapped ion mobility spectrometry
• Rice type 1 non-symbiotic hemoglobin
• Collision cross section
• Unfolding

In this study, for the first time, the conformational space of the rice non-symbiotic hemoglobin type 1 (rHb1) was studied as a function of the starting solution pH using trapped ion mobility spectrometry coupled to mass spectrometry (TIMS-MS) and molecular dynamics. Comparison of the charge state distribution, apo to holo form ratio, and the collision cross section (Omega) profiles as a function of the solution pH showed higher stability of the rHb1 wild-type (WT) when compared with the H73L mutant at mildly acidic conditions. Comparison of the Omega profiles of the rHb1 WT and H73L holo and apo form showed that only the initial unfolding pathways involved the heme cavity, with and without a heme loss, followed by unfolding pathways not necessarily involving the environment of the heme prosthetic group. Candidate structures for the nine transitions observed in the Omega profiles were proposed using molecular dynamic simulations based on the Omega profiles, UV absorption spectroscopy and circular dichroism data as way to describe a potential unfolding pathway. The described unfolding pathway suggests that the rHb1 unfolding is driven by initial distancing of the A, B, and H helices, while the heme cavity and heme group remains intact, followed by the distancing of the E, F, and G helices and subsequent loss of the alpha-helical structure leading to a final random coil conformation.

• 出版日期2018-7