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PhD Exit Seminar – Gianni Castiglione (Chang lab)

October 12, 2016 @ 3:10 pm - 4:10 pm

PhD Exit Seminar

Wednesday October 12th, 3:10 pm – Ramsay Wright Building, Rm. 432


Gianni Castiglione (Chang lab)


“The Evolution of Rhodopsin Structure and Function in Vertebrates”




The visual perception of light is a complex phenomenon, achieved through sophisticated biological systems ranging from the molecular interactions of visual system proteins, to computational processing within retinal neuronal circuits, to the higher cortical synthesis of visual inputs. Through photon absorption, the activation of the rod visual pigment rhodopsin forms the first step in the visual transduction cascade, ultimately mediating all of dim-light organismal visual sensitivity. Natural selection has molded vertebrate rhodopsin into a remarkable molecular machine, with a stunning sensitivity to single photons and an ultra-fast, femtosecond photoproduct formation. These evolutionary innovations are underpinned by the elegant structural and functional features of rhodopsin, which have served as the basis for our understandings of other class A G protein-coupled receptors. The importance of rhodopsin for vision across a diversity of environments makes it an ideal candidate for investigating how natural selection has shaped the molecular evolution of a complex sensory protein’s structure and function. Following a general introduction, Chapter II presents the first evidence for the adaptation of rhodopsin structure and function to cold temperatures, using high altitude Andean catfishes (Siluriformes) as a model system to identify the molecular targets of natural selection. These targets are shown to be highly similar between high altitude Tibetan Plateau and Andean catfish rhodopsins, with evidence in Chapter III supporting the phenotypic convergence of rhodopsin kinetics at high altitudes. In Chapter IV a novel structural feature of rhodopsin is revealed, functioning as a compensatory unit to modulate both rhodopsin spectral sensitivity and light-activated kinetics. This thesis identifies novel features of rhodopsin structure and function, and contributes to the emerging understanding that the structure and function of proteins are inextricably linked to shifts in ecology, environment and the dynamics of molecular evolution.

Ramsay Wright is a wheelchair accessible building.



October 12, 2016
3:10 pm - 4:10 pm
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Ramsay Wright Building, Room 432
25 Harbord St.
Toronto, ON M5S 3G5 Canada