TY - JOUR
T1 - PH-regulated metal-ligand switching in the HM loop of ATP7A
T2 - A new paradigm for metal transfer chemistry
AU - Kline, Chelsey D.
AU - Gambill, Benjamin F.
AU - Mayfield, Mary
AU - Lutsenko, Svetlana
AU - Blackburn, Ninian J.
N1 - Funding Information:
This work was funded by grants from the National Institutes of Health GM115214 (NJB) and P01 GM067166 (N. J. B. and S. L.). We gratefully acknowledge the use of facilities at the Stanford Synchrotron Radiation Lightsource (SSRL), which is supported by the U.S. Department of Energy, Office of Science, and Office of Basic Energy Sciences under Contract No. DE-AC02-76SF00515. The SSRL Structural Molecular Biology Program is supported by the DOE Office of Biological and Environmental Research, the National Institutes of Health, and the National Institute of General Medical Sciences (including P41GM103393).
Publisher Copyright:
© 2016 The Royal Society of Chemistry.
PY - 2016/8
Y1 - 2016/8
N2 - Cuproproteins such as PHM and DBM mature in late endosomal vesicles of the mammalian secretory pathway where changes in vesicle pH are employed for sorting and post-translational processing. Colocation with the P1B-type ATPase ATP7A suggests that the latter is the source of copper and supports a mechanism where selectivity in metal transfer is achieved by spatial colocation of partner proteins in their specific organelles or vesicles. In previous work we have suggested that a lumenal loop sequence located between trans-membrane helices TM1 and TM2 of the ATPase, and containing five histidines and four methionines, acts as an organelle-specific chaperone for metallation of the cuproproteins. The hypothesis posits that the pH of the vesicle regulates copper ligation and loop conformation via a mechanism which involves His to Met ligand switching induced by histidine protonation. Here we report the effect of pH on the HM loop copper coordination using X-ray absorption spectroscopy (XAS), and show via selenium substitution of the Met residues that the HM loop undergoes similar conformational switching to that found earlier for its partner PHM. We hypothesize that in the absence of specific chaperones, HM motifs provide a template for building a flexible, pH-sensitive transfer site whose structure and function can be regulated to accommodate the different active site structural elements and pH environments of its partner proteins.
AB - Cuproproteins such as PHM and DBM mature in late endosomal vesicles of the mammalian secretory pathway where changes in vesicle pH are employed for sorting and post-translational processing. Colocation with the P1B-type ATPase ATP7A suggests that the latter is the source of copper and supports a mechanism where selectivity in metal transfer is achieved by spatial colocation of partner proteins in their specific organelles or vesicles. In previous work we have suggested that a lumenal loop sequence located between trans-membrane helices TM1 and TM2 of the ATPase, and containing five histidines and four methionines, acts as an organelle-specific chaperone for metallation of the cuproproteins. The hypothesis posits that the pH of the vesicle regulates copper ligation and loop conformation via a mechanism which involves His to Met ligand switching induced by histidine protonation. Here we report the effect of pH on the HM loop copper coordination using X-ray absorption spectroscopy (XAS), and show via selenium substitution of the Met residues that the HM loop undergoes similar conformational switching to that found earlier for its partner PHM. We hypothesize that in the absence of specific chaperones, HM motifs provide a template for building a flexible, pH-sensitive transfer site whose structure and function can be regulated to accommodate the different active site structural elements and pH environments of its partner proteins.
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U2 - 10.1039/c6mt00062b
DO - 10.1039/c6mt00062b
M3 - Article
C2 - 27242196
AN - SCOPUS:84982175132
SN - 1756-5901
VL - 8
SP - 729
EP - 733
JO - Metallomics
JF - Metallomics
IS - 8
ER -