Preparation of a gene-engineering mutant of bacteriorhodopsin BR-D96V and corresponding poly(vinyl alcohol)-based functional composite films

Abstract

Bacteriorhodopsin (BR) exhibits, as a membrane protein in Halobacterium salinarum, unique photoresponsive behaviors, and shows promise as a functional information material. A new mutant of BR with the 96th aspartic acid replaced by valine (BR-D96V) was obtained and then a composite film of BR-D96V in a synthetic polymer matrix was prepared in this research. The mutant BR-D96V was expressed in a bacterio-opsin deficient halobacterial strain (L33) by gene engineering. Although valine is very hydrophobic, this point mutant keeps the basic biological activities, namely, photoelectric and photochromic responses. Nevertheless, the lifetime of M intermediate in the BR mutant is nearly two orders of magnitude longer than that of wild-type BR in neutral aqueous solution, which benefits its potential application as an information material. The M lifetime is further significantly prolonged after embedding BR-D96V into poly(vinyl alcohol) (PVA). It was also found that BR-D96V is very sensitive to water content in comparison with wild-type BR and another BR mutant. synthetic polymer, organic photoelectric material, composite film, bacteriorhodopsin, site-specific mutagenesis, photoresponsive protein Citation: Zhao Y C, Ming M, Hong J, et al. Preparation of a gene-engineering mutant of bacteriorhodopsin BR-D96V and corresponding poly(vinyl alcohol)-based functional composite films.

Preparation of a cross-linked gelatin/bacteriorhodopsin film and its photochromic properties

“…Due to the poor processibility of BR itself, one usually embeds BR into a polymeric matrix to obtain a functional composite "material" [5,[9][10][11][12][13][14][15][16][17]. While gelatin/BR films have been a typical kind of BR-containing materials with good mechanical properties and optical transparency [18][19][20], it is very difficult to introduce detergents or strong alkaline substances into the matrix due to the following reasons: if the films are exposed to those environments, the film integrity cannot be kept; or if those substances are added into a suspension of BR and polymer before film formation, the BR proteins are inclined to denature during dehydration to form a film.…”

Purple membrane resists cell adhesion

“…Excitation of BR with a photon causes a photocycle, resulting in uptake of a proton from the cytoplasmic side of the PM and release of another proton to the extracellular side. BR and relevant retinal proteins have attracted much attention as potential optical materials in 2-D or 3-D storage, holographic storage, optical filtering, light switching, neural networks, super-fast photo detection, motion detection and artificial retinas, etc [9][10][11][12] and also as model proteins in fundamental research [13][14][15][16][17][18].…”