1
|
Near IR-plasmon enhanced guided fluorescence and thermal imaging of tissue subsurface target using ICG-labeled gold nanourchin and protein contrast agent: implication of stability. Lasers Med Sci 2022; 37:2145-2156. [PMID: 34993706 DOI: 10.1007/s10103-021-03471-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2021] [Accepted: 11/12/2021] [Indexed: 10/19/2022]
Abstract
A dual-function nanocomposite agent (NCA) was prepared for deep tissue fluorescence and thermal imaging. The results showed that a combination of some agents such as gold nanourchins (GNU) and indocyanine green (ICG) can have spectral overlapping and hence some peak broadening. Despite 83% and 92% loss of NCA fluorescence after tissue layers L1 and L2, respectively, there was sufficient signal detected for imaging the target buried under the tissue. No fluorescence was detected after L3. A significant contribution was made by GNU for both the fluorescence signal due to the plasmon-enhanced fluorescence (PEF) effect and the thermal heating because of local surface plasmon resonance (LSPR) due to its sharp tips. In the first case, PEF occurred within the first 40 s then followed by a gradual quenching by 23% in 4 min and 72% in the following 6 min. During the second quenching time, the emission signal was blue shifted by 10 nm. Of the three samples, sample 2 (S2) indicated the highest temperature rise ≈ 60 °C in 50 s; sample 3 (S3) produced the lowest temperature of ≈ 33 °C in 250 s after the first layer, thus showing BSA acting as a heat sink. Both the heating and cooling time are determined by the thermal properties of the material such as conductivity and diffusivity. Finally, despite the advantages of PEF, the photostability and quenching rate of a dye molecule must be considered in a dynamic detection monitoring system to account and compensate for the effect of contrast agent quality variation.
Collapse
|
2
|
Juneja S, Singh H, Palui S, Trivedi S, Singh SS, Haridas V, Pandey S. Unprecedented Intramolecular Association-Induced Fluorescence in Tryptophan-Conjugated Peptidomimetics. J Phys Chem B 2019; 123:3112-3117. [PMID: 30901217 DOI: 10.1021/acs.jpcb.9b01676] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
We report herewith tryptophan (Trp)-conjugated peptidomimetics that show intramolecular through-space association between the Trp units. Our investigation revealed that the proximal placement of Trp can lead to the emergence of a new and unanticipated fluorescent entity constituting a Trp-Trp dimer. Proton-induced modulation of fluorescence is a consequence of this work. Investigations with control compounds unequivocally revealed that the fluorescence property is not originated from the localized excited state but from the unprecedented Trp-Trp intramolecular dimer in the ground state itself. The present findings will initiate the biophysical scientists to have a relook at the fluorescence properties of Trp-containing proteins.
Collapse
Affiliation(s)
- Shreya Juneja
- Department of Chemistry , Indian Institute of Technology Delhi , Hauz Khas, New Delhi 110016 , India
| | - Hanuman Singh
- Department of Chemistry , Indian Institute of Technology Delhi , Hauz Khas, New Delhi 110016 , India
| | - Sayan Palui
- Department of Chemistry , Indian Institute of Technology Delhi , Hauz Khas, New Delhi 110016 , India
| | - Shruti Trivedi
- Department of Chemistry , Indian Institute of Technology Delhi , Hauz Khas, New Delhi 110016 , India
| | - Sharan S Singh
- Department of Chemistry , Indian Institute of Technology Delhi , Hauz Khas, New Delhi 110016 , India
| | - V Haridas
- Department of Chemistry , Indian Institute of Technology Delhi , Hauz Khas, New Delhi 110016 , India
| | - Siddharth Pandey
- Department of Chemistry , Indian Institute of Technology Delhi , Hauz Khas, New Delhi 110016 , India
| |
Collapse
|
3
|
Exploring the interaction of silver nanoparticles with pepsin and its adsorption isotherms and kinetics. Chem Biol Interact 2018. [DOI: 10.1016/j.cbi.2018.03.004] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
|
4
|
Cote JM, Ramirez-Mondragon CA, Siegel ZS, Czyzyk DJ, Gao J, Sham YY, Mukerji I, Taylor EA. The Stories Tryptophans Tell: Exploring Protein Dynamics of Heptosyltransferase I from Escherichia coli. Biochemistry 2017; 56:886-895. [PMID: 28098447 DOI: 10.1021/acs.biochem.6b00850] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Heptosyltransferase I (HepI) catalyzes the addition of l-glycero-β-d-manno-heptose to Kdo2-Lipid A, as part of the biosynthesis of the core region of lipopolysaccharide (LPS). Gram-negative bacteria with gene knockouts of HepI have reduced virulence and enhanced susceptibility to hydrophobic antibiotics, making the design of inhibitors of HepI of interest. Because HepI protein dynamics are partially rate-limiting, disruption of protein dynamics might provide a new strategy for inhibiting HepI. Discerning the global mechanism of HepI is anticipated to aid development of inhibitors of LPS biosynthesis. Herein, dynamic protein rearrangements involved in the HepI catalytic cycle were probed by combining mutagenesis with intrinsic tryptophan fluorescence and circular dichroism analyses. Using wild-type and mutant forms of HepI, multiple dynamic regions were identified via changes in Trp fluorescence. Interestingly, Trp residues (Trp199 and Trp217) in the C-terminal domain (which binds ADP-heptose) are in a more hydrophobic environment upon binding of ODLA to the N-terminal domain. These residues are adjacent to the ADP-heptose binding site (with Trp217 in van der Waals contact with the adenine ring of ADP-heptose), suggesting that the two binding sites interact to report on the occupancy state of the enzyme. ODLA binding was also accompanied by a significant stabilization of HepI (heating to 95 °C fails to denature the protein when it is in the presence of ODLA). These results suggest that conformational rearrangements, from an induced fit model of substrate binding to HepI, are important for catalysis, and the disruption of these conformational dynamics may serve as a novel mechanism for inhibiting this and other glycosyltransferase enzymes.
Collapse
Affiliation(s)
- Joy M Cote
- Department of Chemistry, Wesleyan University , Middletown, Connecticut 06459, United States
| | | | - Zarek S Siegel
- Department of Chemistry, Wesleyan University , Middletown, Connecticut 06459, United States
| | - Daniel J Czyzyk
- Department of Chemistry, Wesleyan University , Middletown, Connecticut 06459, United States
| | | | | | - Ishita Mukerji
- Molecular Biophysics Program, Department of Molecular Biology and Biochemistry, Wesleyan University , Middletown, Connecticut 06459, United States
| | - Erika A Taylor
- Department of Chemistry, Wesleyan University , Middletown, Connecticut 06459, United States
| |
Collapse
|
5
|
Alexiev U, Farrens DL. Fluorescence spectroscopy of rhodopsins: insights and approaches. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2013; 1837:694-709. [PMID: 24183695 DOI: 10.1016/j.bbabio.2013.10.008] [Citation(s) in RCA: 63] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/01/2013] [Revised: 10/11/2013] [Accepted: 10/16/2013] [Indexed: 01/30/2023]
Abstract
Fluorescence spectroscopy has become an established tool at the interface of biology, chemistry and physics because of its exquisite sensitivity and recent technical advancements. However, rhodopsin proteins present the fluorescence spectroscopist with a unique set of challenges and opportunities due to the presence of the light-sensitive retinal chromophore. This review briefly summarizes some approaches that have successfully met these challenges and the novel insights they have yielded about rhodopsin structure and function. We start with a brief overview of fluorescence fundamentals and experimental methodologies, followed by more specific discussions of technical challenges rhodopsin proteins present to fluorescence studies. Finally, we end by discussing some of the unique insights that have been gained specifically about visual rhodopsin and its interactions with affiliate proteins through the use of fluorescence spectroscopy. This article is part of a Special Issue entitled: Retinal Proteins - You can teach an old dog new tricks.
Collapse
Affiliation(s)
- Ulrike Alexiev
- Physics Department, Freie Universität Berlin, Berlin, Germany.
| | - David L Farrens
- Departments of Biochemistry and Molecular Biology, Oregon Health Sciences University, USA
| |
Collapse
|
6
|
Zhu C, Sun Y, Wang Y, Luo Y, Fan D. The preparation and characterization of novel human-like collagen metal chelates. MATERIALS SCIENCE & ENGINEERING. C, MATERIALS FOR BIOLOGICAL APPLICATIONS 2013; 33:2611-9. [DOI: 10.1016/j.msec.2013.02.028] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/15/2012] [Revised: 01/21/2013] [Accepted: 02/15/2013] [Indexed: 10/27/2022]
|
7
|
Dwivedi AK, Prasad KM, Trivedi V, Iyer PK. Interaction of heme proteins with anionic polyfluorene: insights into physiological effects, folding events, and inhibition activity. ACS APPLIED MATERIALS & INTERFACES 2012; 4:6371-6377. [PMID: 23113839 DOI: 10.1021/am302046n] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
Because of the toxicity caused by the heme redox-active iron proteins, their elevated levels, localization, and accumulation in the brain, many forms of neurodegenerative diseases, such as Alzheimer's disease, Parkinson's disease, and Huntington's disease, occur as a result of which the brain becomes vulnerable to oxidative stress, ultimately resulting in neuronal death. An anionic water-soluble conjugated polyfluorene derivative poly(9,9-bis(6-sulfate hexyl) fluorene-alt-1,4-phenylene) sodium salt (P1) that binds Fe³⁺ proteins with very high selectivity and sensitivity is reported here. The photophysical properties of P1 were modified by the interaction with ferric heme-containing proteins cytochrome c (Cc), methemoglobin (MetHb), and hemin. P1 was found to be highly sensitive toward Fe³⁺ heme proteins as compared to nonmetalloproteins. We observed that the respective activities of ferric heme proteins were inhibited and proteins were unfolded, due to modification in their heme microenvironment in the presence of the polymer P1. The observations reported in this article provide the first example for the use of a water-soluble conjugated polymer in applications, such as (1) to detect small quantities of iron proteins in aqueous medium/physiological condition with the highest K(sv) values of 2.27 × 10⁸ M⁻¹ for Cc, 3.81 × 10⁷ M⁻¹ for MetHb, and 5.31 × 10⁷ M⁻¹ for hemin; (2) to study the physiological effects of heme metalloproteins; (3) to visualize the folding events in real time; and (4) the inhibition activity of metalloproteins can be selectively studied using a conjugated polymer based assay system rapidly without interference from nonmetalloproteins at biological pH. All this is achieved by generating optical events, taking advantage of the bright fluorescence of anionic polyfluorene P1 in this case, that can be observed and monitored by modification in the absorption and emission color in real time.
Collapse
Affiliation(s)
- Atul Kumar Dwivedi
- Department of Chemistry, Indian Institute of Technology Guwahati, Guwahati-781039, India
| | | | | | | |
Collapse
|
8
|
Cloning, expression, purification, and biochemical characterisation of the FIC motif containing protein of Mycobacterium tuberculosis. Protein Expr Purif 2012; 86:58-67. [PMID: 22982230 DOI: 10.1016/j.pep.2012.08.020] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2012] [Revised: 08/28/2012] [Accepted: 08/29/2012] [Indexed: 01/01/2023]
Abstract
The role of FIC (Filamentation induced by cAMP)(2) domain containing proteins in the regulation of many vital pathways, mostly through the transfer of NMPs from NTPs to specific target proteins (NMPylation), in microorganisms, higher eukaryotes, and plants is emerging. The identity and function of FIC domain containing protein of the human pathogen, Mycobacterium tuberculosis, remains unknown. In this regard, M. tuberculosis fic gene (Mtfic) was cloned, overexpressed, and purified to homogeneity for its biochemical characterisation. It has the characteristic FIC motif, HPFREGNGRSTR (HPFxxGNGRxxR), spanning 144th to 155th residue. Neither the His-tagged nor the GST-tagged MtFic protein, overexpressed in Escherichia coli, nor expression of Mtfic in Mycobacterium smegmatis, yielded the protein in the soluble fraction. However, the maltose binding protein (MBP) tagged MtFic (MBP-MtFic) could be obtained partly in the soluble fraction. The cloned, overexpressed, and purified recombinant MBP-MtFic showed conversion of ATP, GTP, CTP, and UTP into AMP, GMP, CMP, and UMP, respectively. Sequence alignment with several FIC motif containing proteins, complemented with homology modeling on the FIC motif containing protein, VbhT of Bartonella schoenbuchensis as the template, showed conservation and interaction of residues constituting the FIC domain. Site-specific mutagenesis of the His144, or Glu148, or Asn150 of the FIC motif, or of Arg87 residue that constitutes the FIC domain, or complete deletion of the FIC motif, abolished the NTP to NMP conversion activity. The design of NMP formation assay using the recombinant, soluble MtFic would enable identification of its target substrate for NMPylation.
Collapse
|
9
|
Müller WEG, Wang X, Binder M, von Lintig J, Wiens M, Schröder HC. Differential expression of the demosponge (Suberites domuncula) carotenoid oxygenases in response to light: protection mechanism against the self-produced toxic protein (Suberitine). Mar Drugs 2012; 10:177-199. [PMID: 22363229 PMCID: PMC3280542 DOI: 10.3390/md10010177] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2011] [Revised: 01/05/2012] [Accepted: 01/09/2012] [Indexed: 11/16/2022] Open
Abstract
The demosponge Suberites domuncula has been described to contain high levels of a proteinaceous toxin, Suberitine, that displays haemolytic activityIn the present study this 7-8 kDa polypeptide has been isolated and was shown to exhibit also cytotoxic effects on cells of the same species. Addition of retinal, a recently identified metabolite of β-carotene that is abundantly present in S. domuncula was found to reduce both the haemolytic and the cell toxic activity of Suberitine at a molar ratio of 1:1. Spectroscopic analyses revealed that the interaction between β-carotene and Suberitine can be ascribed to a reversible energy transfer reaction. The enzyme that synthesises retinal in the sponge system is the β,β-carotene-15,15'-dioxygenase [carotene dioxygenase]. In order to clarify if this enzyme is the only β-carotene-metabolizing enzyme a further oxygenase had been identified and cloned, the (related) carotenoid oxygenase. In contrast to the dioxygenase, the carotenoid oxygenase could not degrade β-carotene or lycopene in Escherichia coli strains that produced these two carotenoids; therefore it had been termed related-carotenoid oxygenase. Exposure of primmorphs to light of different wavelengths from the visible spectrum resulted after 3 days in a strong upregulation of the dioxygenase in those 3D-cell aggregates that had been incubated with β-carotene. The strongest effect is seen with blue light at a maximum around 490 nm. It is concluded that the toxin Suberitine is non-covalently modified by retinal, the cleavage product from β-carotene via the enzyme carotene dioxygenase, a light inducible oxygenase. Hence, this study highlights that in S. domuncula the bioactive metabolite, retinal, has the property to detoxify its homologous toxin.
Collapse
Affiliation(s)
- Werner E. G. Müller
- ERC Advanced Grant Research Group at the Institute for Physiological Chemistry, University Medical Center of the Johannes Gutenberg University Mainz, Duesbergweg 6, Mainz D-55128, Germany; (X.W.); (M.B.); (M.W.); (H.C.S.)
| | - Xiaohong Wang
- ERC Advanced Grant Research Group at the Institute for Physiological Chemistry, University Medical Center of the Johannes Gutenberg University Mainz, Duesbergweg 6, Mainz D-55128, Germany; (X.W.); (M.B.); (M.W.); (H.C.S.)
- National Research Center for Geoanalysis, 26 Baiwanzhuang Dajie, Beijing 100037, China
| | - Michael Binder
- ERC Advanced Grant Research Group at the Institute for Physiological Chemistry, University Medical Center of the Johannes Gutenberg University Mainz, Duesbergweg 6, Mainz D-55128, Germany; (X.W.); (M.B.); (M.W.); (H.C.S.)
| | - Johannes von Lintig
- Department of Pharmacology, Case Western Reserve University, 10900 Euclid Ave., Cleveland, OH 44160, USA;
| | - Matthias Wiens
- ERC Advanced Grant Research Group at the Institute for Physiological Chemistry, University Medical Center of the Johannes Gutenberg University Mainz, Duesbergweg 6, Mainz D-55128, Germany; (X.W.); (M.B.); (M.W.); (H.C.S.)
| | - Heinz C. Schröder
- ERC Advanced Grant Research Group at the Institute for Physiological Chemistry, University Medical Center of the Johannes Gutenberg University Mainz, Duesbergweg 6, Mainz D-55128, Germany; (X.W.); (M.B.); (M.W.); (H.C.S.)
| |
Collapse
|
10
|
Khan MJ, Qayyum S, Alam F, Husain Q. Effect of tin oxide nanoparticle binding on the structure and activity of α-amylase from Bacillus amyloliquefaciens. NANOTECHNOLOGY 2011; 22:455708. [PMID: 22020314 DOI: 10.1088/0957-4484/22/45/455708] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
Proteins adsorbed on nanoparticles (NPs) are being used in biotechnology, biosensors and drug delivery. However, understanding the effect of NPs on the structure of proteins is still in a nascent state. In the present paper tin oxide (SnO2) NPs were synthesized by the reaction of SnCl4·5H2O in methanol via the sol-gel method and characterized by x-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR) and transmission electron microscopy (TEM). The binding of these SnO2-NPs with α-amylase was investigated by using UV-vis, fluorescence and circular dichroism (CD) spectroscopic techniques. A strong quenching of tryptophan fluorescence intensity in α-amylase was observed due to formation of a ground state complex with SnO2-NPs. Far-UV CD spectra showed that the secondary structure of α-amylase was changed in the presence of NPs. The Michaelis-Menten constant (K(m)), was found to be 26.96 and 28.45 mg ml(-1), while V(max) was 4.173 and 3.116 mg ml(-1) min(-1) for free and NP-bound enzyme, respectively.
Collapse
Affiliation(s)
- Mohammad Jahir Khan
- Department of Biochemistry, Faculty of Life Sciences, Aligarh Muslim University, Aligarh-202002, India
| | | | | | | |
Collapse
|
11
|
Imhof N, Kuhn A, Gerken U. Substrate-Dependent Conformational Dynamics of the Escherichia coli Membrane Insertase YidC. Biochemistry 2011; 50:3229-39. [DOI: 10.1021/bi1020293] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Nora Imhof
- Institute of Microbiology, University of Hohenheim, Garbenstrasse 30, D-70599 Stuttgart, Germany
| | - Andreas Kuhn
- Institute of Microbiology, University of Hohenheim, Garbenstrasse 30, D-70599 Stuttgart, Germany
| | - Uwe Gerken
- Institute of Microbiology, University of Hohenheim, Garbenstrasse 30, D-70599 Stuttgart, Germany
| |
Collapse
|
12
|
Lacerda SHDP, Park JJ, Meuse C, Pristinski D, Becker ML, Karim A, Douglas JF. Interaction of gold nanoparticles with common human blood proteins. ACS NANO 2010; 4:365-79. [PMID: 20020753 DOI: 10.1021/nn9011187] [Citation(s) in RCA: 688] [Impact Index Per Article: 49.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/19/2023]
Abstract
In order to better understand the physical basis of the biological activity of nanoparticles (NPs) in nanomedicine applications and under conditions of environmental exposure, we performed an array of photophysical measurements to quantify the interaction of model gold NPs having a wide range of NP diameters with common blood proteins. In particular, absorbance, fluorescence quenching, circular dichroism, dynamic light scattering, and electron microscopy measurements were performed on surface-functionalized water-soluble gold NPs having a diameter range from 5 to 100 nm in the presence of common human blood proteins: albumin, fibrinogen, gamma-globulin, histone, and insulin. We find that the gold NPs strongly associate with these essential blood proteins where the binding constant, K, as well as the degree of cooperativity of particle--protein binding (Hill constant, n), depends on particle size and the native protein structure. We also find tentative evidence that the model proteins undergo conformational change upon association with the NPs and that the thickness of the adsorbed protein layer (bare NP diameter <50 nm) progressively increases with NP size, effects that have potential general importance for understanding NP aggregation in biological media and the interaction of NP with biological materials broadly.
Collapse
Affiliation(s)
- Silvia H De Paoli Lacerda
- Center for Biological Evaluation and Research, Food and Drug Administration, Bethesda, Maryland 20892, USA.
| | | | | | | | | | | | | |
Collapse
|
13
|
Dzhemesyuk OA, Antipin SA, Gostev FE, Fedorovich IB, Sarkisov OM, Ostrovskii MA. Energy transfer from tryptophane amino acid residues to retinal in a bacteriorhodopsin molecule within a femtosecond timescale. DOKL BIOCHEM BIOPHYS 2002; 382:46-9. [PMID: 11938670 DOI: 10.1023/a:1014411424849] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Affiliation(s)
- O A Dzhemesyuk
- Emanuel Institute of Biochemical Physics, Russian Academy of Sciences, ul. Kosygina 4, Moscow, 117977 Russia
| | | | | | | | | | | |
Collapse
|
14
|
Jang DJ, van den Berg R, El-Sayed M. Absence of tryptophan fluorescence quenching by metal cations in delipidated bacteriorhodopsin. FEBS Lett 2001. [DOI: 10.1016/0014-5793(90)80571-y] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
|
15
|
Taneva S, Jordanova N, Petkanchin I. Electro-optical investigation of lipid-depleted purple membranes. Biophys Chem 1992. [DOI: 10.1016/0301-4622(92)85041-2] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
|
16
|
Wu S, Chang Y, el-Sayed MA, Marti T, Mogi T, Khorana HG. Effects of tryptophan mutation on the deprotonation and reprotonation kinetics of the Schiff base during the photocycle of bacteriorhodopsin. Biophys J 1992; 61:1281-8. [PMID: 1318094 PMCID: PMC1260391 DOI: 10.1016/s0006-3495(92)81936-7] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Abstract
The rates of deprotonation and reprotonation of the protonated Schiff base (PSB) are determined during the photocycle of nine bacteriorhodopsin mutants in which Trp-10, 12, 80, 86, 137, 138, 182 and 189 are individually substituted by either phenylalanine or cysteine. Of all the mutants, the replacement of Trp-86, Trp-182, and Trp-189 by phenylalanine and Trp-137 by cysteine is found to significantly alter the rate of the deprotonation, but not that of the reprotonation process. As compared with ebR, the Trp-86 mutation dramatically increases the rate of deprotonation of the PSB while the Trp-182 mutation greatly decreases this rate. Temperature dependence studies on the rate constants of the deprotonation demonstrate that the different energetic and entropic effects of the mutation are responsible for the observed different kinetic behavior of the Trp-86 and Trp-182 mutants as compared with that of ebR. In the case of Trp-86 mutant, a large decrease in both energy and entropy of activation suggests that the mutation of this tryptophan residue opens up the protein structure as a result of eliminating the hydrogen-bonding group on its side chain by a phenylalanine substitution. A correlation is observed between the proton pumping yield and the relative amplitudes of the slow deprotonation component but not with rate constants of the rise or decay process at constant pH. These results are best discussed in terms of the heterogeneity model (with parallel cycle) rather than back reaction model.
Collapse
Affiliation(s)
- S Wu
- Department of Chemistry and Biochemistry, University of California, Los Angeles 90024
| | | | | | | | | | | |
Collapse
|
17
|
Wu SG, Jang DJ, el-Sayed MA, Marti T, Mogi T, Gobind Khorana H. The use of tryptophan mutants in identifying the 296 nm transient absorbing species during the photocycle of bacteriorhodopsin. FEBS Lett 1991; 284:9-14. [PMID: 2060632 DOI: 10.1016/0014-5793(91)80749-s] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
The transient absorption at 296 nm was part of the spectroscopic evidence that initiated the proposal that tyrosinate (Tyr-) is formed during, and important to, the photocycle of bacteriorhodopsin (bR). Recent evidence against such a proposal comes from the results of NMR, UV Raman as well as electron cryo-microscopic structural studies. This makes it credible to assign this absorption to a charge perturbation of the lowest energy absorption of one of the tryptophan (Trp) residues in bR. The transient absorption at 296 nm is examined for each of 8 tryptophan mutants in which Trp is substituted by phenylalanine or cysteine, which absorb at shorter wavelength. It is shown that while all go through the photocycle, all but Trp-182 mutant show this transient absorption. This strongly suggests the assignment of this absorption to a charge perturbaton of the lowest energy absorption of Trp-182 during the photocycle. The chemical identity of the perturbing charge(s) is briefly discussed.
Collapse
Affiliation(s)
- S G Wu
- Department of Chemistry and Biochemistry, University of California-Los Angeles 90024
| | | | | | | | | | | |
Collapse
|
18
|
Jang DJ, el-Sayed MA, Stern LJ, Mogi T, Khorana HG. Effect of genetic modification of tyrosine-185 on the proton pump and the blue-to-purple transition in bacteriorhodopsin. Proc Natl Acad Sci U S A 1990; 87:4103-7. [PMID: 2349220 PMCID: PMC54055 DOI: 10.1073/pnas.87.11.4103] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
The retinylidene chromophore mutant (Y185F) of bacteriorhodopsin, in which Tyr-185 is substituted by phenylalanine, is examined and compared with wild-type bacteriorhodopsin expressed in Escherichia coli; both were reinstituted similarly in vesicles. The Y185F mutant shows (at least) two distinct spectra at neutral pH. Upon light absorption, the blue species (which absorbs in the red) behaves as if "dead"--i.e., neither its tyrosine nor its protonated Schiff base undergoes deprotonation nor does its tryptophan fluorescence undergo quenching. This result is unlike either the purple species (which absorbs in the blue) or wild-type bacteriorhodopsin expressed in E. coli. As the pH increases, both the color changes and the protonated Schiff base deprotonation efficiency suggest a blue-to-purple transition of the Y185F mutant near pH 9. If this blue-to-purple transition of Y185F corresponds to the blue-to-purple transition of purple-membrane (native) bacteriorhodopsin (occurring at pH 2.6) and of wild-type bacteriorhodopsin expressed in E. coli (occurring at pH 5), the protein-conformation changes of this transition as well as the protonated Schiff base deprotonation may be controlled not by surface pH alone, but rather by the coupling between surface potential and the general protein internal structure around the active site. The results also suggest that Tyr-185 does not deprotonate during the photocycle in purple-membrane bacteriorhodopsin.
Collapse
Affiliation(s)
- D J Jang
- Department of Chemistry and Biochemistry, University of California, Los Angeles 90024
| | | | | | | | | |
Collapse
|