ABSTRACT
The FeoB family proteins are widely distributed prokaryotic membrane proteins involved in Fe(2+) uptake. FeoB consists of N-terminal cytosolic and C-terminal transmembrane domains. The N-terminal region of the cytosolic domain is homologous to small GTPase (G) proteins and is considered to regulate Fe(2+) uptake. The spacer region connecting the G and TM domains reportedly functions as a GDP dissociation inhibitor (GDI)-like domain that stabilizes the GDP-binding state. However, the function of the G and GDI-like domains in iron uptake remains unclear. Here, we report the structural and functional analyses of the FeoB cytosolic domain from Thermotoga maritima. The structure-based mutational analysis indicated that the interaction between the G and GDI-like domains is important for both the GDI and Fe(2+) uptake activities. On the basis of these results, we propose a regulatory mechanism of Fe(2+) uptake.
Subject(s)
Cation Transport Proteins/chemistry , Guanine Nucleotide Dissociation Inhibitors/chemistry , Iron/metabolism , Membrane Transport Proteins/chemistry , Monomeric GTP-Binding Proteins/chemistry , Thermotoga maritima/enzymology , Binding Sites , Cation Transport Proteins/metabolism , Guanine Nucleotide Dissociation Inhibitors/metabolism , Membrane Transport Proteins/metabolism , Models, Biological , Models, Molecular , Monomeric GTP-Binding Proteins/metabolism , Protein Conformation , Thermotoga maritima/metabolism , rho-Specific Guanine Nucleotide Dissociation InhibitorsABSTRACT
FeoB-family proteins are widely distributed in bacteria and archaea and are involved in high-affinity Fe(2+) uptake through the plasma membrane. FeoB consists of an N-terminal cytosolic region followed by a C-terminal transmembrane region. The cytosolic region contains small GTPase and GDP dissociation inhibitor-like domains, which serve a regulatory function. The truncated cytosolic region of the iron transporter FeoB from Thermotoga maritima was overexpressed, purified and crystallized. Four native or SeMet crystal forms in a nucleotide-free state or in complex with either GDP or GMPPNP diffracted to resolutions of between 1.5 and 2.1 A.