Mapping protein matrix cavities in human cytoglobin through Xe atom binding.
Cytoglobin is the fourth recognized globin type, almost ubiquitously distributed in human tissues; its function is still poorly understood. Cytoglobin displays a core region of about 150 residues, structurally related to hemoglobin and myoglobin, and two extra segments, about 20 residues each, at the N- and C-termini. The core region hosts a large apolar cavity, held to provide a ligand diffusion pathway to/from the heme, and/or ligand temporary docking sites. Here we report the crystal structure (2.4A resolution, R-factor 19.1%) of a human cytoglobin mutant bearing the CysB2(38) --> Ser and CysE9(83) --> Ser substitutions (CYGB*), treated under pressurized xenon. Three Xe atoms bind to the heme distal site region of CYGB* mapping the protein matrix apolar cavity. Despite the conserved globin fold, the cavity found in CYGB* is structured differently from those recognized to play a functional role in myoglobin, neuroglobin, truncated hemoglobins, and Cerebratulus lacteus mini-hemoglobin.
de Sanctis
Daniele
D
Department of Physics-INFM and Centre for Excellence in Biomedical Research, University of Genova, Via Dodecaneso 33, Genoa I-16146, Italy.
Dewilde
Sylvia
S
Pesce
Alessandra
A
Moens
Luc
L
Ascenzi
Paolo
P
Hankeln
Thomas
T
Burmester
Thorsten
T
Bolognesi
Martino
M
D001665:Binding Sites; D003198:Computer Simulation; D018360:Crystallography, X-Ray; D000078842:Cytoglobin; D005914:Globins; D006418:Heme / Q000737:chemistry*; D006801:Humans; D046911:Macromolecular Substances; D008958:Models, Molecular; D010544:Peroxidases / Q000737:chemistry*; D016062:Porosity; D011485:Protein Binding; D011487:Protein Conformation; D014978:Xenon / Q000737:chemistry*
C000627265:CYGB protein, human; D000078842:Cytoglobin; D046911:Macromolecular Substances; D014978:Xenon; D006418:Heme; D005914:Globins; D010544:Peroxidases