Hydrophobic pockets at the membrane interface: an original mechanism for membrane protein interactions.
The effect of partial digestion by trypsin and GluC protease on the association of the membrane polypeptides of LH1 from Rhodospirillum (Rsp.) rubrum was studied. Trypsin and GluC protease treatments of LH1 result in the cleavage of the first three amino acids from the alpha polypeptide and of the first 18 amino acids from the beta polypeptide, respectively, without any noticeable reorganization of their secondary structure, as measured by attenuated total reflectance Fourier transform IR spectroscopy. However, the enthalpy variation accompanying dimer formation was dramatically reduced by the protease attacks by as much as 80%. Our results show that the alphabeta heterodimer is mainly stabilized by hydrophobic interactions which involve the amino-terminal extensions of the participating polypeptides. Using the close homology between the polypeptides of Rsp. rubrum LH1 and that of Rsp. molischianum LH2, whose structure is known, a structural model for these "hydrophobic pockets" lying close to the membrane interface is proposed.
Arluison
Véronique
V
Service de Biophysique des Fonctions Membranaires, DBJC/CEA and URA 2096 CNRS, CE Saclay, 91191 Gif/Yvette Cedex, France. Veronique.Arluison@ibpc.fr
Seguin
Jérôme
J
Le Caer
Jean-Pierre
JP
Sturgis
James N
JN
Robert
Bruno
B
D000595:Amino Acid Sequence; D001425:Bacterial Outer Membrane Proteins / Q000737:chemistry* / Q000378:metabolism*; D001426:Bacterial Proteins / Q000737:chemistry / Q000378:metabolism; D006868:Hydrolysis; D057927:Hydrophobic and Hydrophilic Interactions; D045342:Light-Harvesting Protein Complexes / Q000737:chemistry* / Q000378:metabolism*; D008969:Molecular Sequence Data; D009994:Osmolar Concentration; D021122:Protein Subunits / Q000737:chemistry / Q000378:metabolism; D012242:Rhodobacter sphaeroides; D012241:Rhodopseudomonas; D012247:Rhodospirillum rubrum; D017386:Sequence Homology, Amino Acid; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization; D013053:Spectrophotometry; D017550:Spectroscopy, Fourier Transform Infrared; D013816:Thermodynamics; D014357:Trypsin / Q000737:chemistry
C118800:B800-820 light-harvesting complex, Rhodopseudomonas acidophila; D001425:Bacterial Outer Membrane Proteins; D001426:Bacterial Proteins; D045342:Light-Harvesting Protein Complexes; D021122:Protein Subunits; D014357:Trypsin