scholarly journals Effects of Cone Connexin-36 Disruption on Light Adaptation and Circadian Regulation of the Photopic ERG

2020 ◽  
Vol 61 (6) ◽  
pp. 24
Author(s):  
Shuo Zhang ◽  
Polina Lyuboslavsky ◽  
Jendayi Azeezah Dixon ◽  
Micah A. Chrenek ◽  
Jana T. Sellers ◽  
...  
Keyword(s):  
Light Adaptation ◽  
Circadian Regulation ◽  
Connexin 36 ◽  
Photopic Erg

Connexin 36 in bovine retina: Lack of phosphorylation but evidence for association with phosphorylated proteins

2003 ◽  
Vol 20 (4) ◽  
pp. 385-395 ◽  
Author(s):  
ARI SITARAMAYYA ◽  
JOHN W. CRABB ◽  
DIANE F. MATESIC ◽  
ALEXANDER MARGULIS ◽  
VINITA SINGH ◽  
...  
Keyword(s):  
Gap Junctions ◽  
Gap Junction ◽  
Cyclic Nucleotide ◽  
Visual Information ◽  
Information Transfer ◽  
Light Adaptation ◽  
Connexin 36 ◽  
Phosphorylated Proteins ◽  
Bovine Retina ◽  
Cone Pathway

In vertebrate retina interneuronal communication through gap junctions is involved in light adaptation and in the transfer of visual information from the rod pathway to the cone pathway. Reports over the last two decades have indicated that these gap junctions are regulated by cyclic nucleotide-dependent protein kinases suggesting that the gap junction proteins, connexins, are phosphorylated. Though all the connexins involved in light adaptation and information transfer from rod to cone pathway are not yet known, connexin 36 has been shown to be definitively involved in the latter process. We have therefore attempted to investigate the cyclic nucleotide-dependent phosphorylation of this connexin in bovine retina. We found several soluble and membrane proteins in bovine retina whose phosphorylation was regulated by cyclic nucleotides. However, no protein of about 36 kDa with cyclic nucleotide-regulated phosphorylation was found in gap junction-enriched membrane preparations. A 36-kDa phosphorylated protein was found in gap junction-enriched membranes phosphorylated in the presence of calcium. However, this protein was not immunoprecipitated by anti-connexin 36 antibodies indicating that it was not connexin 36 in spite of its similarity in molecular weight. Immunoprecipitation did reveal phosphorylated proteins coimmunoprecipitated with connexin 36. Two of these proteins were identified as beta and alpha tubulin subunits. Though cyclic GMP and calcium did not greatly influence the association of these proteins with connexin 36, the results suggest the possibility of connexin 36 associating with other proteins. Together, these observations indicate that interneuronal communication at gap junctions made by connexin 36 may not be regulated by direct phosphorylation of connexin 36, but possibly by phosphorylation of associated proteins.

A Hydrogen Bond Between Linear Tetrapyrrole and Conserved Aspartate Causes the Far-Red Shifted Absorption of Phytochrome Photoreceptors

2020 ◽  
Author(s):  
Egle Maximowitsch ◽  
Tatiana Domratcheva
Keyword(s):  
Hydrogen Bond ◽  
Light Adaptation ◽  
Positive Charge ◽  
Pyrrole Ring ◽  
Md Simulations ◽  
Spectral Shift ◽  
Specific Domain ◽  
Study Guides ◽  
Rational Engineering ◽  
Tuning Mechanism

Photoswitching of phytochrome photoreceptors between red-absorbing (Pr) and far-red absorbing (Pfr) states triggers light adaptation of plants, bacteria and other organisms. Using quantum chemistry, we elucidate the color-tuning mechanism of phytochromes and identify the origin of the Pfr-state red-shifted spectrum. Spectral variations are explained by resonance interactions of the protonated linear tetrapyrrole chromophore. In particular, hydrogen bonding of pyrrole ring D with the strictly conserved aspartate shifts the positive charge towards ring D thereby inducing the red spectral shift. Our MD simulations demonstrate that formation of the ring D–aspartate hydrogen bond depends on interactions between the chromophore binding domain (CBD) and phytochrome specific domain (PHY). Our study guides rational engineering of fluorescent phytochromes with a far-red shifted spectrum.

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