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首页> 外文期刊>Biochemistry >Color-Changing Mutation in the E−F Loop of Proteorhodopsin
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Color-Changing Mutation in the E−F Loop of Proteorhodopsin

机译：视紫红质蛋白EF环中的变色突变

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It is usually assumed that only amino acids located near the retinal chromophore arenresponsible for color tuning of rhodopsins. However, we recently found that replacement of Ala178nwith Arg in the E-F loop of proteorhodopsin (PR), an archaeal-type rhodopsin in marine bacteria,nshifts the λmax from 525 to 545 nm at neutral pH [Yoshitsugu,M., Shibata,M., Ikeda, D., Furutani,nY., and Kandori, H. (2008) Angew. Chem., Int. Ed. 47, 3923-3926]. Since the location of Ala178 isndistant from the retinal chromophore (∼25 A), the molecular mechanism of the unusual mutationneffect on color tuning is intriguing.Herewe studied thismechanismby using additionalmutations andnsome analytical methods. Introduction of Arg into the corresponding amino acid in bacteriorho-ndopsin (BR, M163R mutant) does not change the absorption spectra, indicating that the effect isnspecific to PR. Introduction of Arg into the A-BorC-Dloop yields little (3 nm) or no color change,nrespectively.T177Rand P180Rmutants exhibited absorption spectra identical to that of thewild type,nwhile N176R and S179R mutants exhibit λmax values of 528 and 535 nm, respectively. Therefore, thenobserved color change is position-specific, being fully effective at position 178 and half-effective atnposition 179. Salt affects the absorption spectra of wild-type and A178R PR similarly. FTIRnspectroscopy at 77 K indicated similar chromophore structures for wild-type and A178R PR, andnA178RPRpumps protons normally.We infer that the E-F loop has a unique structure in PRand thenmutation of Ala178 disrupts the structure that includes the transmembrane region, leading to thenobserved changes in color and pKa
机译：通常认为，视紫红质的颜色调整仅负责视网膜发色团附近的氨基酸。然而，我们最近发现在海洋细菌中的古细菌型视紫红质蛋白视紫红质（PR）的EF环中，用Arg替代Ala178n会使λmax在中性pH下从525 nm改变到545 nm [Yoshitsugu，M。，Shibata，M。]。 ，池田，D.，Furutani，n。和Kandori，H.（2008）Angew。 Chem。，Int。埃德47，3923-3926]。由于Ala178的位置与视网膜发色团（约25 A）距离较远，因此异常突变对色彩调节的影响的分子机制令人着迷。在此，我们通过使用其他突变和一些分析方法研究了这种机制。将Arg引入细菌视紫红质（BR，M163R突变体）的相应氨基酸中不会改变吸收光谱，表明该作用对PR不具有特异性。分别将Arg引入A-BorC-Dloop几乎不会产生（3 nm）的颜色变化。T177R和P180R突变体的吸收光谱与野生型相同，而N176R和S179R突变体的λmax值分别为528和535 nm。 。因此，观察到的颜色变化是位置特定的，在位置178处完全有效，在位置179处完全有效。盐对野生型和A178R PR的吸收光谱有相似的影响。 FTIR光谱在77 K时表明野生型和A178R PR和nA178RPR泵质子的发色团结构正常。我们推断EF环在PR中具有独特的结构，然后Ala178的突变破坏了包括跨膜区域的结构，从而观察到颜色的变化和pKa

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