Our laboratory is interested in the structure and function
of G protein-coupled receptors with particular focus on
the subgroup of receptors known as visual pigments. The
pigments are major components of rod and cone photoreceptor
cells and form the basis of phototransduction in the vertebrate
retina. As is typical of G protein-coupled receptors, the
visual pigments are integral membrane proteins composed
of seven transmembrane helical segments. However, what is
atypical is that each pigment is bound covalently to a small
molecule ligand, 11-cis-retinal, which is a chromophore
for the absorption of light.
Spectral Tuning: There are four visual pigments in
the human retina: rhodopsin, the pigment of rod photoreceptor
cells, and the blue, green and red color vision pigments
of cone photoreceptor cells. These four pigments have
absorption spectra which span (actually define) the
visible region of the electromagnetic spectrum. And
yet, the small molecule chromophore responsible for
absorption of light is the same in each pigment. One
of the goals of our research is to understand the
underlying mechanism by which the spectrum of each
pigment is “tuned” by interactions of
the retinal chromophore with amino acid side chains
in the active site of the proteins.
Mechanism of Retinal Disease: A large number of mutations
in rhodopsin are known to cause inherited diseases
of the retina. We are interested in a small group
of these which result in constitutive activation of
rhodopsin - that is, these mutations cause the protein
to activate the G protein transducin in the absence
of light. The activating mutations are known to cause
two different diseases: a devastating degenerative
disease of the retina known as retinitis pigmentosa
and, in comparison, a relatively benign disease known
as congenital stationary night blindness. Our goal
is to elucidate the underlying molecular mechanisms
responsible for pathophysiology in these diseases.
To do this, we employ a broad array of techniques
ranging from classical biochemistry and mutagenesis
for in vitro characterization of the mutant proteins
to the development of transgenic animals combined
with single-cell electrophysiology to test models
of disease under in vivo conditions.
Structure of the Active State: Rhodopsin is the only
G protein-coupled receptor for which a structure has
been determined by x-ray crystallography. While the
structure of rhodopsin has had an enormous impact
on our understanding of the protein it is clear that
we are at the very beginning of these structural studies
and major questions remain. In particular, we still
do not have a structure for the active conformation
of the protein – the published rhodopsin structure
is for the inactive- or dark-state. Our laboratory
is currently undertaking a major effort to determine
the x-ray crystal structure of the active state of
rhodopsin. In addition, we are undertaking efforts
to determine the crystal structure of other G protein-coupled
Selected Recent Publications:
Kumar RP, Morehouse BR, Matos JO, Malik K, Lin H, Krauss IJ and Oprian DD (2017). "Structural Characterization of Early Michaelis Complexes in the Reaction Catalyzed by (+)-Limonene Synthase from Citrus sinensis Using Fluorinated Substrate Analogues." Biochemistry. 56 (12), pp 1706–1715.
Morehouse BR, Kumar RP, Matos JO, Olsen SN, Entova S and Oprian DD (2017). "Functional and Structural Characterization of a (+)-Limonene Synthase from Citrus sinensis."Biochemistry. 56 (12), pp 1706–1715.
Chakrabarti KS, Agafonov RV, Pontiggia F, Otten R, Higgins MK, Schertler GF, Oprian DD and Kern D (2016). "Conformational Selection in a Protein-Protein Interaction Revealed by Dynamic Pathway Analysis." Cell Rep 14(1): 32-42.
Devine EL, Theobald DL and Oprian DD (2016). "Relocating the Active-Site Lysine in Rhodopsin: 2. Evolutionary Intermediates." Biochemistry 55(34): 4864-4870
Kumar RP, Ranaghan MJ, Ganjei AY and Oprian DD (2015). "Crystal Structure of Recoverin with Calcium Ions Bound to Both Functional EF Hands." Biochemistry 54(49): 7222-7228.
D'Antona AM, Xie G, Sligar SG and Oprian DD (2014). "Assembly of an activated rhodopsin-transducin complex in nanoscale lipid bilayers." Biochemistry 53(1): 127-134.
Devine EL, Oprian DD and Theobald DL (2013). "Relocating the active-site lysine in rhodopsin and implications for evolution of retinylidene proteins." Proc Natl Acad Sci U S A 110(33): 13351-13355.
Ranaghan MJ, Kumar RP, Chakrabarti KS, Buosi V, Kern D and Oprian DD (2013). "A highly conserved cysteine of neuronal calcium-sensing proteins controls cooperative binding of Ca2+ to recoverin." J Biol Chem 288(50): 36160-36167.
Deupi X, Edwards P, Singhal A, Nickle B, Oprian DD, Schertler G and Standfuss J (2012). "Stabilized G protein binding site in the structure of constitutively active metarhodopsin-II." Proc Natl Acad Sci U S A 109(1): 119-124.
Frederiksen R, Boyer NP, Nickle B, Chakrabarti KS, Koutalos Y, Crouch RK, Oprian D and Cornwall MC (2012). "Low aqueous solubility of 11-cis-retinal limits the rate of pigment formation and dark adaptation in salamander rods." Journal of General Physiology 139(6): 493-505.
Standfuss J, Edwards PC, D'Antona A, Fransen M, Xie G, Oprian DD and Schertler GF (2011). "The structural basis of agonist-induced activation in constitutively active rhodopsin." Nature 471(7340): 656-660.
Xie G, D'Antona AM, Edwards PC, Fransen M, Standfuss J, Schertler GF and Oprian DD (2011). "Preparation of an activated rhodopsin/transducin complex using a constitutively active mutant of rhodopsin." Biochemistry 50(47): 10399-10407.
Standfuss J, Xie G, Edwards PC, Burghammer M, Oprian DD, Schertler GF (2007). "Crystal structure of a thermally stable rhodopsin mutant." J Mol Biol. 2007 Oct 5;372(5):1179-88.
Bayburt TH, Leitz AJ, Xie G, Oprian DD, Sligar SG (2007). " Transducin activation by nanoscale lipid bilayers containing one and two rhodopsins." J Biol Chem. 2007 May 18;282(20):14875-81.
Chen J, Shi G, Concepcion FA, Xie G, Oprian D, Chen J (2006). "Stable rhodopsin/arrestin complex leads to retinal degeneration in a transgenic mouse model of autosomal dominant retinitis pigmentosa." J Neurosci. 2006 Nov 15;26(46):11929-37.
Higgins MK, Oprian DD, Schertler GF (2006). "Recoverin binds exclusively
to an amphipathic peptide at the N terminus of rhodopsin kinase,
inhibiting rhodopsin phosphorylation without affecting catalytic
activity of the kinase." J Biol Chem. 2006 Jul 14;281 (28):19426-32.
Tam BM, Xie G, Oprian DD, Moritz OL (2006). "Mislocalized rhodopsin
does not require activation to cause retinal degeneration and
neurite outgrowth in Xenopus laevis." J Neurosci. 2006 Jan
Kono M, Crouch RK, Oprian DD (2005). "A dark and constitutively
active mutant of the tiger salamander UV pigment." Biochemistry.
Kim JM, Altenbach C, Kono M, Oprian DD, Hubbell WL, Khorana HG
(2004). "Structural origins of constitutive activation in rhodopsin:
Role of the K296/E113 salt bridge." Proc Natl Acad Sci USA. 101(34):12508-13.
Das J, Crouch RK, Ma JX, Oprian DD, Kono M (2004). "Role of the
9-methyl group of retinal in cone visual pigments." Biochemistry.
Jin S, Cornwall MC, Oprian DD (2003). "Opsin activation as a cause of
congenital night blindness." Nat Neurosci. 6:731-5.
Jin S, McKee TD, Oprian DD (2003). "An improved rhodopsin/EGFP
fusion protein for use in the generation of transgenic Xenopus
laevis." FEBS Lett. 542(1-3):142-6.
Oprian DD (2003). "Phototaxis, chemotaxis and the missing link." Trends Biochem Sci. 28:167-9.
Gross AK, Rao VR, Oprian DD (2003). "Characterization of rhodopsin
congenital night blindness mutant T94I." Biochemistry. 42:2009-15.
Gross AK, Xie G, Oprian DD (2003). "Slow binding of retinal to
rhodopsin mutants G90D and T94D." Biochemistry. 42:2002-8.
Xie G, Gross AK, Oprian DD (2003). "An opsin mutant with increased
thermal stability." Biochemistry. 42:1995-2001.
View Complete Publication List on PubMed: Daniel Oprian
Last update: April 3, 2017