Inter-helical hydrogen bonds are essential elements for intra-protein signal transduction: the role of Asp115 in bacteriorhodopsin transport function.
The behavior of the D115A mutant was analyzed by time-resolved UV-Vis and Fourier transformed infrared (FTIR) spectroscopies, aiming to clarify the role of Asp115 in the intra-protein signal transductions occurring during the bacteriorhodopsin photocycle. UV-Vis data on the D115A mutant show severely desynchronized photocycle kinetics. FTIR data show a poor transmission of the retinal isomerization to the chromoprotein, evidenced by strongly attenuated helical changes (amide I), the remarkable absence of environment alterations and protonation/deprotonation events related to Asp96 and direct Schiff base (SB) protonation form the bulk. This argues for the interactions of Asp115 with Leu87 (via water molecule) and Thr90 as key elements for the effective and vectorial proton path between Asp96 and the SB, in the cytoplasmic half of bacteriorhodopsin. The results strongly suggest the presence of a regulation motif enclosed in helices C and D (Thr90-Pro91/Asp115) which drives properly the dynamics of helix C through a set of interactions. It also supports the idea that intra-helical hydrogen bonding clusters in the buried regions of transmembrane proteins can be potential elements in intra-protein signal transduction.
Perálvarez-Marín
Alex
A
Unitat de Biofísica, Departament de Bioquímica i de Biologia Molecular, Facultat de Medicina, and Centre d'Estudis en Biofísica, Universitat Autònoma de Barcelona, Bellaterra (Cerdanyola del Vallès), Barcelona 08193, Spain. alex.peralvarez@dbb.su.se
Lórenz-Fonfría
Víctor A
VA
Bourdelande
José-Luís
JL
Querol
Enric
E
Kandori
Hideki
H
Padrós
Esteve
E
D020816:Amino Acid Motifs; D019943:Amino Acid Substitution; D001224:Aspartic Acid / Q000737:chemistry* / Q000235:genetics; D001436:Bacteriorhodopsins / Q000737:chemistry* / Q000235:genetics / Q000502:physiology; D019617:Halobacterium salinarum / Q000378:metabolism / Q000528:radiation effects; D006860:Hydrogen Bonding; D008027:Light; D008958:Models, Molecular; D017433:Protein Structure, Secondary; D021381:Protein Transport; D018717:Purple Membrane / Q000378:metabolism / Q000528:radiation effects; D015398:Signal Transduction; D017550:Spectroscopy, Fourier Transform Infrared; D014867:Water / Q000378:metabolism
D014867:Water; D001224:Aspartic Acid; D001436:Bacteriorhodopsins