%0 Journal Article
%A Draganova, Elizabeth
B.
%A Akbas, Neval
%A Adrian, Seth A.
%A Lukat-Rodgers, Gudrun S.
%A Collins, Daniel P.
%A Dawson, John H.
%A Allen, Courtni E.
%A Schmitt, Michael P.
%A Rodgers, Kenton R.
%A Dixon, Dabney W.
%D 2015
%T Heme Binding by Corynebacterium diphtheriae HmuT: Function and Heme Environment
%U https://acs.figshare.com/articles/journal_contribution/Heme_Binding_by_i_Corynebacterium_diphtheriae_i_HmuT_Function_and_Heme_Environment/2115688
%R 10.1021/acs.biochem.5b00666.s001
%2 https://acs.figshare.com/ndownloader/files/3749308
%K WT
%K heme pocket residue mutants
%K Y 235 side
%K Heme EnvironmentThe heme uptake pathway
%K H 136A Y 235A
%K hydrogen bond acceptor
%K Hemoglobin utilization assays
%K ferric HmuT
%K H 136
%K M 292A Characterization
%K Y 235 ligand
%K Corynebacterium diphtheriae HmuT
%K hydrogen bond donor
%K H 136A HmuT
%K FeCO Raman shifts
%K Ferrous Y 235A
%K ABC transporter HmuUV
%K Y 235A
%K H 136 side
%X The
heme uptake pathway (hmu) of Corynebacterium diphtheriae utilizes multiple proteins to bind and transport heme into the cell.
One of these proteins, HmuT, delivers heme to the ABC transporter
HmuUV. In this study, the axial ligation of the heme in ferric HmuT
is probed by examination of wild-type (WT) HmuT and a series of conserved
heme pocket residue mutants, H136A, Y235A, and M292A. Characterization
by UV–visible, resonance Raman, and magnetic circular dichroism
spectroscopies indicates that H136 and Y235 are the axial ligands
in ferric HmuT. Consistent with this assignment of axial ligands,
ferric WT and H136A HmuT are difficult to reduce while Y235A is reduced
readily in the presence of dithionite. The FeCO Raman shifts in WT,
H136A, and Y235A HmuT–CO complexes provide further evidence
of the axial ligand assignments. Additionally, these frequencies provide
insight into the nonbonding environment of the heme pocket. Ferrous
Y235A and the Y235A–CO complex reveal that the imidazole of
H136 exists in two forms, one neutral and one with imidazolate character,
consistent with a hydrogen bond acceptor on the H136 side of the heme.
The ferric fluoride complex of Y235A reveals the presence of at least
one hydrogen bond donor on the Y235 side of the heme. Hemoglobin utilization
assays showed that the axial Y235 ligand is required for heme uptake
in HmuT.
%I ACS Publications