The solute carrier SPNS2 recruits PI(4,5)P to synergistically regulate transport of sphingosine-1-phosphate.

Solute carrier spinster homolog 2 (SPNS2), one of only four known major facilitator superfamily (MFS) lysolipid transporters in humans, exports sphingosine-1-phosphate (S1P) across cell membranes. Here, we explore the synergistic effects of lipid binding and conformational dynamics on SPNS2's transport mechanism. Using mass spectrometry, we discovered that SPNS2 interacts preferentially with PI(4,5)P.

Studies on an iron(iii)-peroxo porphyrin. Iron(III)-peroxo or iron(II)-superoxo?

We demonstrate that a one electron reduced product of the heme iron dioxygen adduct exists in solution not only as the commonly accepted iron(iii)-peroxo species, but coexists with its isomeric iron(ii)-superoxo form. This unusual reduced metal-superoxide adduct [M(ii)-O(2)(-)] is recently reported as a reactive intermediate in the case of non-heme extradiol dioxygenases and could also be generated by cryoreduction of a heme Fe(II)-O(2) adduct. The existence of iron(ii)-superoxo species in solution is consistent with IR, EPR, mass and Mössbauer spectra.