2M8C: The solution NMR structure of E. coli apo-HisJ

Escherichia coli HisJ is a type II periplasmic binding protein that functions to reversibly capture histidine and transfer it to its cognate inner membrane ABC permease. Here, we used NMR spectroscopy to determine the structure of apo-HisJ (26.5 kDa) in solution. HisJ is a bilobal protein in which domain 1 (D1) is made up of two noncontiguous subdomains, and domain 2 (D2) is expressed as the inner domain. To better understand the roles of D1 and D2, we have isolated and characterized each domain separately. Structurally, D1 closely resembles its homologous domain in apo- and holo-HisJ, whereas D2 is more similar to the holo-form. NMR relaxation experiments reveal that HisJ becomes more ordered upon ligand binding, whereas isolated D2 experiences a significant reduction in slower (millisecond to microsecond) motions compared with the homologous domain in apo-HisJ. NMR titrations reveal that D1 is able to bind histidine in a similar manner as full-length HisJ, albeit with lower affinity. Unexpectedly, isolated D1 and D2 do not interact with each other in the presence or absence of histidine, which indicates the importance of intact interdomain-connecting elements (i.e. hinge regions) for HisJ functioning. Our results shed light on the binding mechanism of type II periplasmic binding proteins where ligand is initially bound by D1, and D2 plays a supporting role in this dynamic process.
PDB ID: 2M8CDownload
MMDB ID: 114221
PDB Deposition Date: 2013/5/15
Updated in MMDB: 2013/11
Experimental Method:
solution nmr
Source Organism:
Similar Structures:
Biological Unit for 2M8C: monomeric; determined by author
Molecular Components in 2M8C
Label Count Molecule
Protein (1 molecule)
Cationic Amino Acid ABC Transporter, Periplasmic Binding Protein
Molecule annotation
* Click molecule labels to explore molecular sequence information.

Citing MMDB