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PubMed1986

The upper and lower limits of the mechanistic stoichiometry of mitochondrial oxidative phosphorylation. Stoichiometry of oxidative phosphorylation.

Determination of the intrinsic or mechanistic P/O ratio of oxidative phosphorylation is difficult because of the unknown magnitude of leak fluxes. Applying a new approach developed to overcome this problem (see our preceding paper in this journal), the relationships between the rate of O2 uptake [( Jo)3], the net rate of phosphorylation (Jp), the P/O ratio, and the respiratory control ratio (RCR) have been determined in rat liver mitochondria when the rate of phosphorylation was systematically varied by three specific means. (a) When phosphorylation is titrated with carboxyatractyloside, linear relationships are observed between Jp and (Jo)3. These data indicate that the upper limit of the mechanistic P/O ratio is 1.80 for succinate and 2.90 for 3-hydroxybutyrate oxidation. (b) Titration with malonate or antimycin yields linear relationships between Jp and (Jo)3. These data give the lower limit of the mechanistic P/O ratio of 1.63 for succinate and 2.66 for 3-hydroxybutyrate oxidation. (c) Titration with a protonophore yields linear relationships between Jp, (Jo)3, and (Jo)4 and between P/O and 1/RCR. Extrapolation of the P/O ratio to 1/RCR = 0 yields P/O ratios of 1.75 for succinate and 2.73 for 3-hydroxybutyrate oxidation which must be equal to or greater than the mechanistic stoichiometry. When published values for the H+/O and H+/ATP ejection ratios are taken into consideration, these measurements suggest that the mechanistic P/O ratio is 1.75 for succinate oxidation and 2.75 for NADH oxidation.

Adenosine Triphosphate↗
PubMed1983

3',5'-cyclic adenosine monophosphate- and Ca2+-calmodulin-dependent endogenous protein phosphorylation activity in membranes of the bovine chromaffin secretory vesicles: identification of two phosphorylated components as tyrosine hydroxylase and protein kinase regulatory subunit type II.

Membranes of the secretory vesicles from bovine adrenal medulla were investigated for the presence of the endogenous protein phosphorylation activity. Seven phosphoprotein bands in the molecular weight range of 250,000 to 30,000 were observed by means of the sodium dodecyl sulphate electrophoresis and autoradiography. On the basis of the criteria of molecular weight, selective stimulation of the phosphorylation by cyclic AMP (as compared with cyclic GMP) and immunoprecipitation by specific antibodies, band 5 (molecular weight 60,300) was found to represent the phosphorylated form of the secretory vesicle-bound tyrosine hydroxylase. The electrophoretic mobility, the stimulatory and inhibitory effects of cyclic AMP in presence of Mg2+ and Zn,2+ respectively, and immunoreactivity toward antibodies showed band 6 to contain two forms of the regulatory subunits of the type II cyclic AMP-dependent protein kinase, distinguishable by their molecular weights (56,000 and 52,000, respectively). Phosphorylation of band 7 (molecular weight 29,800) was stimulated about 2 to 3 times by Ca2+ and calmodulin in the concentration range of both agents believed to occur in the secretory tissues under physiological conditions.

Adrenal Medulla↗
PubMed1993

Developmental changes in tau phosphorylation: fetal tau is transiently phosphorylated in a manner similar to paired helical filament-tau characteristic of Alzheimer's disease.

Rat and human fetal brain tau were probed with a panel of monoclonal antibodies (tau-1, AT8, 8D8, RT97, SMI31, SMI34) that distinguish between paired helical filament (PHF)-tau of Alzheimer's disease and normal adult brain tau. These antibodies discriminate between normal and PHF-tau because their epitopes are phosphorylated in PHF-tau. Although only one molecular isoform of tau was shown to be expressed in fetal brain, two fetal tau species could be distinguished on sodium dodecyl sulfate-polyacrylamide gel electrophoresis and the slower migrating species was recognized by all of the PHF-tau-specific antibodies. Moreover, this immunoreactivity was shown to be phosphorylation dependent. Our observations suggest that the abnormal phosphorylation of tau in Alzheimer's disease may be the result of reactivation of pathways governing the phosphorylation of tau in the developing brain.

Adult↗
PubMed2003

Cilostazol prevents tumor necrosis factor-alpha-induced cell death by suppression of phosphatase and tensin homolog deleted from chromosome 10 phosphorylation and activation of Akt/cyclic AMP response element-binding protein phosphorylation.

This study examines the signaling mechanism by which cilostazol prevents neuronal cell death. Cilostazol ( approximately 0.1-100 microM) prevented tumor necrosis factor-alpha (TNF-alpha)-induced decrease in viability of SK-N-SH and HCN-1A cells, which was antagonized by 1 microM iberiotoxin, a maxi-K channel blocker. TNF-alpha did not suppress the viability of the U87-MG cell, a phosphatase and tensin homolog deleted from chromosome 10 (PTEN)-null glioblastoma cell, but it did decrease viability of U87-MG cells transfected with expression vectors for the sense PTEN, and this decrease was also prevented by cilostazol. Cilostazol as well as 1,3-dihydro-1-[2-hydroxy-5-(trifluoromethyl)phenyl]-5-(trifluoromethyl)-2H-benzimidazol-2-one (NS-1619) and (3S)(+)-(5-chloro-2-methoxyphenyl)-1,3-dihydro-3-fluoro-6-(trifluoromethyl)-2H-indole-2-one (BMS 204352), maxi-K channel openers, prevented increased DNA fragmentation evoked by TNF-alpha, which were antagonizable by iberiotoxin. TNF-alpha-induced increased PTEN phosphorylation and decreased Akt/cyclic AMP response element-binding protein (CREB) phosphorylation were significantly prevented by cilostazol, those of which were antagonized by both iberiotoxin and paxilline, maxi-K channel blockers. The same results were evident in U87-MG cells transfected with expression vectors for sense PTEN. Cilostazol increases the K+ current in SK-N-SH cells by activating maxi-K channels without affecting the ATP-sensitive K+ channel. Thus, our results for the first time provide evidence that cilostazol prevents TNF-alpha-induced cell death by suppression of PTEN phosphorylation and activation of Akt/CREB phosphorylation via mediation of the maxi-K channel opening.

Cell Death↗
PubMed2006

Epstein-Barr virus protein kinase BGLF4 is a virion tegument protein that dissociates from virions in a phosphorylation-dependent process and phosphorylates the viral immediate-early protein BZLF1.

Epstein-Barr virus (EBV) BGLF4 is a viral protein kinase that is expressed in the lytic phase of infection and is packaged in virions. We report here that BGLF4 is a tegument protein that dissociates from the virion in a phosphorylation-dependent process. We also present evidence that BGLF4 interacts with and phosphorylates BZLF1, a key viral regulator of lytic infection. These conclusions are based on the following observations. (i) In in vitro tegument release assays, a significant fraction of BGLF4 was released from virions in the presence of physiological NaCl concentrations. (ii) Addition of physiological concentrations of ATP and MgCl(2) to virions enhanced BGLF4 release, but phosphatase treatment of virions significantly reduced BGLF4 release. (iii) A recombinant protein containing a domain of BZLF1 was specifically phosphorylated by purified recombinant BGLF4 in vitro, and BGLF4 altered BZLF1 posttranslational modification in vivo. (iv) BZLF1 was specifically coimmunoprecipitated with BGLF4 in 12-O-tetradecanoylphorbol-13-acetate-treated B95-8 cells and in COS-1 cells transiently expressing both of these viral proteins. (v) BGLF4 and BZLF1 were colocalized in intranuclear globular structures, resembling the viral replication compartment, in Akata cells treated with anti-human immunoglobulin G. Our results suggest that BGLF4 functions not only in lytically infected cells by phosphorylating viral and cellular targets but also immediately after viral penetration like other herpesvirus tegument proteins.

Cell Line↗
PubMed1999

Induced focal adhesion kinase (FAK) expression in FAK-null cells enhances cell spreading and migration requiring both auto- and activation loop phosphorylation sites and inhibits adhesion-dependent tyrosine phosphorylation of Pyk2.

Focal adhesion kinase (FAK) is a nonreceptor protein tyrosine kinase involved in integrin-mediated control of cell behavior. Following cell adhesion to components of the extracellular matrix, FAK becomes phosphorylated at multiple sites, including tyrosines 397, 576, and 577. Tyr-397 is an autophosphorylation site that promotes interaction with c-Src or Fyn. Tyr-576 and Tyr-577 lie in the putative activation loop of the kinase domain, and FAK catalytic activity may be elevated through phosphorylation of these residues by associated Src family kinase. Recent studies have implicated FAK as a positive regulator of cell spreading and migration. To further study the mechanism of adhesion-induced FAK activation and the possible role and signaling requirements for FAK in cell spreading and migration, we utilized the tetracycline repression system to achieve inducible expression of either wild-type FAK or phosphorylation site mutants in fibroblasts derived from FAK-null mouse embryos. Using these Tet-FAK cells, we demonstrated that both the FAK autophosphorylation and activation loop sites are critical for maximum adhesion-induced FAK activation and FAK-enhanced cell spreading and migration responses. Negative effects on cell spreading and migration, as well as decreased phosphorylation of the substrate p130(Cas), were observed upon induced expression of the FAK autophosphorylation site mutant. These negative effects appear to result from an inhibition of integrin-mediated signaling by the FAK-related kinase Pyk2/CAKbeta/RAFTK/CadTK.

3T3 Cells↗
PubMed2003

Strategies and solid-phase formats for the analysis of protein and peptide phosphorylation employing a novel fluorescent phosphorylation sensor dye.

Protein kinases represent one of the largest families of regulatory enzymes, with more than 2,000 of them being encoded for by the human genome. Many cellular processes are regulated by the reversible phosphorylation of proteins and upwards of 30% of the proteins comprising the eukaryotic proteome are likely to be phosphorylated at some point during their existence. In the past, analysis of global protein phosphorylation has been accomplished through radiolabelling of samples with inorganic (32P or [gamma-32)P] ATP. The approach is limited to specimens amenable to radiolabelling and poses certain safety and disposal problems. Alternatively, immunodetection with antibodies to the common phosphoamino acids may be employed, but the antibodies are relatively expensive and exhibit limited specificity and a certain degree of cross-reactivity. Pro-Q Diamond dye is a new fluorescent phosphosensor technology suitable for the detection of phosphoserine-, phosphothreonine- and phosphotyrosine-containing proteins directly in isoelectric focusing gels, SDS-polyacrylamide gels and two-dimensional gels. Additionally, the technology is appropriate for the detection of phosphoproteins or phosphopeptides arrayed on protein chips or affixed to beads. Dye-stained proteins and peptides can be excited with a laser-based light source of 532 or 543 nm or with a xenon-arc lamp-based system equipped with appropriate band pass filters. Alternatively, ultraviolet light of about 302 nm may be employed, providing that sufficiently long exposure times are used to collect the fluorescence signal. Pro-Q Diamond dye emits maximally at approximately 580 nm. The fluorescence-based detection technology is easy to conduct, cost effective and allows rapid large-scale screening of protein and peptide phosphorylation in a variety of solid-phase assay formats.

Electrophoresis, Polyacrylamide Gel↗
PubMed2001

Serine/threonine phosphorylation of IRS-1 triggers its degradation: possible regulation by tyrosine phosphorylation.

Insulin receptor substrate (IRS)-1 protein expression is markedly reduced in many insulin-resistant states, although the mechanism for this downregulation is unclear. In this study, we have investigated the early events in the insulin pathway that trigger the degradation of IRS-1. Incubation of the adipocytes with insulin induced a fast electrophoretic mobility shift of IRS-1 and a subsequent degradation of the protein. Wortmannin and rapamycin blocked this mobility shift of IRS-1, maintained the insulin-induced tyrosine phosphorylation of IRS-1, and blocked its degradation. In contrast, a glycogen synthase kinase 3 inhibitor, a mitogen-activated protein kinase/extracellular-regulated kinase inhibitor, and various protein kinase C inhibitors had no effect. Incubation with okadaic acid increased the serine/threonine phosphorylation of IRS-1 and its degradation, mimicking insulin, and its effect was prevented by the proteasome inhibitor lactacystin, as well as by rapamycin. Treatment of the cells with the tyrosine phosphatase inhibitor orthovanadate in the presence of insulin or okadaic acid partially inhibited the degradation of IRS-1. We propose that a rapamycin-dependent pathway participates as a negative regulator of IRS-1, increasing its serine/threonine phosphorylation, which triggers degradation. Thus, regulation of serine/threonine versus tyrosine phosphorylation may modulate IRS-1 degradation, affecting insulin sensitivity.

3T3 Cells↗
PubMed2002

A therapeutic CD4 monoclonal antibody inhibits TCR-zeta chain phosphorylation, zeta-associated protein of 70-kDa Tyr319 phosphorylation, and TCR internalization in primary human T cells.

The molecular mechanisms mediating the inhibitory effects of a humanized CD4 mAb YHB.46 on primary human CD4(+) T cells were investigated. Preincubation of T cells with soluble YHB.46 caused a general inhibition of TCR-stimulated protein tyrosine phosphorylation events, including a reduction in phosphorylation of p95(vav), linker for activation of T cells, and Src homology 2 domain-containing leukocyte protein of 76-kDa signaling molecules. A marked reduction in activation of the Ras/mitogen-activated protein kinase pathway was also observed. Examination of the earliest initiation events of TCR signal transduction showed that YHB.46 inhibited TCR-zeta chain phosphorylation together with recruitment and tyrosine phosphorylation of the zeta-associated protein of 70-kDa tyrosine kinase, particularly at Tyr(319), as well as reduced recruitment of p56(lck) to the TCR-zeta and zeta-associated protein of 70-kDa complex. These inhibitory events were associated with inhibition of TCR endocytosis. Our results show that the YHB.46 mAb is a powerful inhibitor of the early initiating events of TCR signal transduction.

Antibodies, Monoclonal↗
PubMed2006

Doxorubicin binds to un-phosphorylated form of hNopp140 and reduces protein kinase CK2-dependent phosphorylation of hNopp140.

Human nucleolar phosphoprotein p140 (hNopp140) is a nucleolar phosphoprotein that can bind to doxorubicin, an anti-cancer agent. We have examined the interaction between hNopp140 and doxorubicin as well as the folding property of hNopp140. Also, the effects of ATP and phosphorylation on the affinity of hNopp140 to doxorubicin are investigated by affinity dependent co-precipitation and surface plasmon resonance methods. Doxorubicin preferentially binds to un-phosphorylated form of hNopp140 with a KD value of 3.3 x 10(-7) M. Furthermore, doxorubicin reduces the protein kinase CK2-dependent phosphorylation of hNopp140, indicating that doxorubicin may perturb the cellular function of hNopp140 by reducing the protein kinase CK2-dependent phosphorylation of hNopp140. Low contents of the secondary structures of hNopp140 and the fast rate of proteolysis imply that hNopp140 has a high percentage of flexible regions or extended loop structures.

CDC2 Protein Kinase↗
PubMed1999

Phosphorylation of a low-molecular-weight polypeptide in rat liver mitochondria and dependence of its phosphorylation on mitochondrial functional state.

We show that incubation of rat liver mitochondria in the presence of [gamma-32P]ATP results in cAMP-dependent phosphorylation of a low-molecular-weight (3.5-kD) polypeptide (LMWP). This component is tightly bound to the mitochondrial membrane. It is not released into solution after freezing and subsequent thawing of the mitochondrial suspension and does not incorporate 32P from [gamma-32P]ATP in the presence of uncouplers of oxidative phosphorylation. Inhibition of adenine nucleotide transport into the mitochondrial matrix by carboxyatractyloside suppresses phosphorylation of the LMWP. Moderate Ca2+ loading of mitochondria increases both phosphorylation and dephosphorylation of the LMWP. Chelation of Ca2+ by incubation in the presence of EGTA suppresses incorporation of 32P into the LMWP.

Adenosine Triphosphate↗
PubMed2003

Phosphorylation of beta-catenin at S33, S37, or T41 can occur in the absence of phosphorylation at T45 in colon cancer cells.

Several previous studies in a variety of systems have suggested that phosphorylation at S45 of beta-catenin is essential for subsequent phosphorylation at more NH(2)-terminal residues. Using genetic models expressing beta-catenin under endogenous regulation, we find that phosphorylation of beta-catenin at S45 is not required for phosphorylation at residues S33, S37, or T41 in human colon cancer cells, in contrast to prevailing models. These findings suggest that there are important cell- and organism-specific differences in even the most highly conserved signaling pathways and emphasize the importance of examining these pathways in the cancer cell types in which the pathways are actually deregulated.

Colonic Neoplasms↗
PubMed1991

Phosphorylation of the beta subunit of casein kinase II in human A431 cells. Identification of the autophosphorylation site and a site phosphorylated by p34cdc2.

To examine the phosphorylation of casein kinase II in cells, the enzyme was isolated by immunoprecipitation from metabolically labeled human epidermal carcinoma A431 cells using polyclonal antipeptide antibodies specific for either the alpha subunit or the beta subunit of the enzyme. When isolated from 32P-labeled cells, the beta subunit was found to be significantly labeled on serine residues whereas only minimal labeling was associated with the alpha subunit. In vitro, the beta subunit of purified bovine casein kinase II was autophosphorylated, also on serine residues. Cleavage of the beta subunit, that had been autophosphorylated in vitro, at tryptophan 9 and tryptophan 12 using N-chlorosuccinimide demonstrated that the autophosphorylation site is located near the amino terminus of the protein, most likely at serine 2 and serine 3. Two-dimensional maps of phosphopeptides generated by digestion of the beta subunit with endoproteinase Glu-C indicted that the majority of the phosphate that was incorporated into the protein in cells was at sites that were indistinguishable from the sites that were autophosphorylated in vitro. In addition to phosphorylation at the autophosphorylation site, the beta subunit is also phosphorylated at an additional site, serine 209, in intact cells. This residue, which is near the carboxyl terminus of the protein, can be phosphorylated in vitro by p34cdc2.

Amino Acid Sequence↗
PubMed1990

Interleukin 2-induced tyrosine phosphorylation. Interleukin 2 receptor beta is tyrosine phosphorylated.

Interaction of interleukin 2 (IL2) with its high affinity membrane receptor complex (IL2R) is sufficient to induce proliferation of T lymphocytes. However, the biochemical mechanisms by which IL2 induces this process remain unresolved. The IL2R complex consists of at least two distinct polypeptides that bind IL2, a 75-kDa intermediate affinity subunit (IL2R beta) and a 55-kDa low affinity subunit (IL2R alpha). As indicated by Western blotting with anti-phosphotyrosine-specific antibodies and confirmed by phosphoamino acid analysis, we now demonstrate that interaction of the T cell growth factor interleukin 2 (IL2) with its high affinity receptor on IL2-sensitive human peripheral blood lymphoblasts induces tyrosine phosphorylation of proteins of 92, 80, 78, 70-75, and 57 kDa. IL2 induced tyrosine phosphorylation in YT 2C2 cells which express only the 75-kDa intermediate affinity IL2 binding molecule (IL2R beta) but not in cells which either express only the 55-kDa low affinity IL2 receptor molecule (IL2R alpha) or no IL2-binding sites. Therefore, IL2R beta, in the absence of IL2R alpha, appears sufficient to transduce the transmembrane signal leading to tyrosine phosphorylation. Two different antibodies reactive with phosphotyrosine specifically immunoprecipitated IL2R beta cross-linked to radiolabeled IL2. These findings suggest that IL2R beta is a substrate for the tyrosine kinase which is activated by IL2 binding to its receptor. Thus, like several other growth factor receptors, activation of the IL2R results in an increase in tyrosine phosphorylation with the receptor itself serving as one substrate.

Amino Acids↗
PubMed1986

Effects of permeant buffers on the initiation of photosynchronous phosphorylation and postillumination phosphorylation in chloroplasts.

Under canonical chemiosmotic formulations, the development of a delocalized transmembrane proton gradient should precede and, in the absence of a membrane potential, should account for all the capacity of an energy transducing system to synthesize ATP. Furthermore, any agents, such as permeant proton-absorbing buffers, that slow down the kinetics of the development of this gradient should, consequently, delay ATP synthesis. We have studied the very early (0 through 1000 ms) steps of photosynthetic ATP synthesis utilizing real-time, rapid flow-quench techniques. We have investigated the effect(s) that permeant buffers exert on this process where these buffers show no uncoupling effects, and the transmembrane potential has been collapsed by valinomycin and K+. Experimentally this system was dissected into two ATP synthesizing components, as follows: synthesis of ATP strictly concomitant with light influx and unaffected by the addition of permeant buffers. We refer to this as photosynchronous phosphorylation and synthesis of ATP monitored after the light was extinguished and which was greatly diminished by the addition of proton-absorbing permeant buffers, thus exhibiting the characteristics of conventional postillumination phosphorylation, and we suggest that it represents part of capacitance phosphorylation. The potential for capacitance phosphorylation initiates very rapidly under light and gradually builds up to steady-state level, and it is governed by canonical chemiosmotic principles. We estimate that its contribution to overall ATP yield is minimal during the first few cycles of the system and that it increases gradually towards steady state when it contributes to the majority of ATP synthesized. Neither a delocalized transmembrane proton gradient nor a strictly localized intramembrane proton pathway can account for these observations so we have proposed that a gating mechanism exists which delivers intramembrane protons initially directly to the ATP synthetase complex but subsequently to the lumen as well, and thus, allows the lumen to act as a capacitor during the steady state. This study can reconcile the findings of Ort et al. (Ort, D. R., Dilley, R. A., and Good, N. E. (1976) Biochim. Biophys. Acta 449, 108-124) with the contrasting findings of Vinkler et al. (Vinkler, C., Avron, M., and Boyer, P. D. (1980) J. Biol. Chem. 255, 2263-2266) through the opposite effects which osmotic strength and KCl concentration exert on the two ATP synthetic phases (during and after illumination) of the rapid flash technique used in those studies.(ABSTRACT TRUNCATED AT 400 WORDS)

Adenosine Triphosphate↗
PubMed1986

[Phosphorylation as a method of regulating inorganic pyrophosphatase activity in E. coli. I. Phosphorylation and enzyme activation induced by ATP].

ATP phosphorylates the regulatory center of E. coli inorganic pyrophosphatase with the resultant 1,5-fold increase in the activity of the enzyme. The maximal incorporation of the ATP gamma-group into pyrophosphatase is 3 moles per mole of the protein. Pi likewise phosphorylates the enzyme regulatory center and lowers the pyrophosphatase activity by 10-15%. The ATP- and Pi-mediated phosphorylation processes are interrelated; ATP prevents phosphorylation by Pi and brings about rapid dephosphorylation of Pi-modified protein.

Adenosine Triphosphate↗
PubMed1986

Structure-catalytic activity relationships of dicyclohexylcarboxamidine analogs in phosphorylation and alkylation of nucleosides by a two-step phosphorylating agent, 2-methylthio-4H-1,3,2-benzodioxaphosphorin 2-oxide (MTBO).

Adenosine borate complex was phosphorylated and o-hydroxybenzylated by 2-methylthio-4H-1,3,2-benzodioxaphosphorin 2-oxide (MTBO) in the presence of 4-morpholine-N,N'-dicyclohexylcarboxamidine (MDC) at first to give 1-(o-hydroxybenzyl)adenosine derivative followed by the rearrangement of the benzyl group to the N-6 amino group to give N6-(o-hydroxybenzyl)adenosine 5'-S-methyl phosphorothiolate. More than 20 analogs of MDC were examined for their catalytic activity in phosphorylation and o-hydroxybenzylation of ribonucleoside by MTBO. Dicyclohexylformamidine (DCF) and n-alkylamino analogs of MDC had no effect on the o-hydroxybenzylation of ribonucleoside by MTBO, but had great effect on the phosphorylation. Dialkylamino and cyclic imino analogs of MDC had high catalytic activities to the both reaction. The dicyclohexylcarboxamidine structure of MDC gave the catalytic ability for phosphorylation by MTBO, while the morpholine moiety had great effect on the selectivity of o-hydroxybenzylation by MTBO.

Adenosine↗
PubMed1987

A phosphorylation-sensitive anti-rhodopsin monoclonal antibody reveals light-induced phosphorylation of rhodopsin in the photoreceptor cell body.

Rho-1C5, a monoclonal antibody sensitive to phosphorylation of rhodopsin, bound to the retinal photoreceptor cell body region of dark-adapted but not light-adapted 8 to 13-day-old-rats. There was no cell body labeling visible either before or after this time, although the photoreceptor outer segments were labeled at all times from postnatal day 5 (PN5) onwards, in both light and dark adapted retinas. However, opsin was detectable in the photoreceptor cell body region from birth onwards using another rhodopsin antibody binding to a site unaffected by phosphorylation. Competitive inhibition radioimmunoassays also indicated light-dependent differences in Rho-1C5 binding at PN8 and adult. Biochemical studies showed light-dependent phosphorylation of rhodopsin at PN8, PN13 (just after eye opening) and adult. These data indicate that rhodopsin can be phosphorylated in a light-regulated manner early in development before eye opening and imply that photoactive chromophores can attach to opsin in the cell body as well as the outer segment.

Animals↗