Characterization of the monomeric form of the transmembrane and cytoplasmic domains of the integrin beta 3 subunit by NMR spectroscopy.
We have characterized a membrane protein containing residues P688-T762 of the integrin beta3 subunit, encompassing its transmembrane and cytoplasmic domains, by nuclear magnetic resonance spectroscopy. Under conditions in which it is monomeric in dodecylphosphocholine micelles, the protein consists mainly of alpha-helical structures. An amino-terminal helix corresponding to the beta3 transmembrane helix extends into the membrane-proximal region of the cytoplasmic domain. Moreover, following an apparent hinge at residues H722-D723, residues K725-A735 are mostly alpha-helical. In the presence of membrane-mimicking detergents, the cytoplasmic domain connected to the transmembrane helix is substantially ordered at pH 4.8 and 50 degrees C. Its carboxyl-terminal end takes on a turn-helix configuration characteristic of the immunoreceptor tyrosine-based activation motif. These structural features of the beta3 subunit should help to explain its interaction with numerous cytosolic interacting proteins and begin to illuminate the mechanism of integrin activation.
Li
Renhao
R
Department of Biochemistry and Biophysics, Johnson Research Foundation, University of Pennsylvania School of Medicine, Philadelphia, PA 19104, USA.
Babu
Charles R
CR
Valentine
Kathleen
K
Lear
James D
JD
Wand
A Joshua
AJ
Bennett
Joel S
JS
DeGrado
William F
WF
D000595:Amino Acid Sequence; D001665:Binding Sites; D002942:Circular Dichroism; D003593:Cytoplasm / Q000737:chemistry*; D006358:Hot Temperature; D006863:Hydrogen-Ion Concentration; D039661:Integrin beta3 / Q000737:chemistry*; D008565:Membrane Proteins / Q000138:chemical synthesis / Q000737:chemistry*; D008823:Micelles; D008969:Molecular Sequence Data; D019906:Nuclear Magnetic Resonance, Biomolecular / Q000379:methods; D010767:Phosphorylcholine / Q000031:analogs & derivatives* / Q000737:chemistry; D019039:Platelet Glycoprotein GPIIb-IIIa Complex / Q000138:chemical synthesis / Q000737:chemistry; D011487:Protein Conformation; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D021122:Protein Subunits / Q000138:chemical synthesis / Q000737:chemistry*; D011993:Recombinant Fusion Proteins / Q000138:chemical synthesis; D013816:Thermodynamics
D039661:Integrin beta3; D008565:Membrane Proteins; D008823:Micelles; D019039:Platelet Glycoprotein GPIIb-IIIa Complex; D021122:Protein Subunits; D011993:Recombinant Fusion Proteins; D010767:Phosphorylcholine; C028810:dodecylphosphocholine