The highly dynamic oligomeric structure of bradavidin II is unique among avidin proteins

Bradavidin II is a biotin‐binding protein from Bradyrhizobium japonicum that resembles chicken avidin and bacterial streptavidin. A biophysical characterization was carried out using dynamic light scattering, native mass spectrometry, differential scanning calorimetry, and isothermal titration calor...

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Published in:Protein science 2013-07, Vol.22 (7), p.980-994
Main Authors: Leppiniemi, Jenni, Meir, Amit, Kähkönen, Niklas, Kukkurainen, Sampo, Määttä, Juha A., Ojanen, Markus, Jänis, Janne, Kulomaa, Markku S., Livnah, Oded, Hytönen, Vesa P.
Format: Article
Language:English
Subjects:
Amino Acid Sequence
Animals
Biotin - chemistry
Biotin - metabolism
Carrier Proteins - chemistry
Carrier Proteins - metabolism
Chickens
Crystal structure
dynamic structure
Hydrogen-Ion Concentration
ligand binding
Ligands
Models, Molecular
Molecular Sequence Data
oligomeric state
Protein Binding
Protein Multimerization
Protein Unfolding
Proteins
Sequence Alignment
structural cooperativity
Temperature
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Summary:Bradavidin II is a biotin‐binding protein from Bradyrhizobium japonicum that resembles chicken avidin and bacterial streptavidin. A biophysical characterization was carried out using dynamic light scattering, native mass spectrometry, differential scanning calorimetry, and isothermal titration calorimetry combined with structural characterization using X‐ray crystallography. These observations revealed that bradavidin II differs from canonical homotetrameric avidin protein family members in its quaternary structure. In contrast with the other avidins, bradavidin II appears to have a dynamic (transient) oligomeric state in solution. It is monomeric at low protein concentrations but forms higher oligomeric assemblies at higher concentrations. The crystal structure of bradavidin II revealed an important role for Phe42 in shielding the bound ligand from surrounding water molecules, thus functionally replacing the L7,8 loop essential for tight ligand binding in avidin and streptavidin. This bradavidin II characterization opens new avenues for oligomerization‐independent biotin‐binding protein development. PDB Code(s): Bradavidin II apo Form‐A, 4GGR Bradavidin II apo Form‐B, 4GGT Bradavidin II biotin‐complex, 4GGZ
ISSN:0961-8368
1469-896X
DOI:10.1002/pro.2281