2BV2

beta gamma crystallin from Ciona Intestinalis

Summary for 2BV2

• Entry DOI: 10.2210/pdb2bv2/pdb
• Descriptor: CIONA BETAGAMMA-CRYSTALLIN, CALCIUM ION, ACETATE ION, ... (5 entities in total)
• Functional Keywords: crystallin, calcium binding, eye lens, spherulin, chordate, ascidian
• Biological source: CIONA INTESTINALIS (SEA SQUIRT)
• Total number of polymer chains: 2
• Total formula weight: 18443.21

Authors

Shimeld, S.M.,Purkiss, A.G.,Dirks, R.P.H.,Bateman, O.A.,Slingsby, C.,Lubsen, N.H. (deposition date: 2005-06-21, release date: 2005-09-29, Last modification date: 2023-12-13)

Primary citation

Shimeld, S.M.,Purkiss, A.G.,Dirks, R.P.H.,Bateman, O.A.,Slingsby, C.,Lubsen, N.H.
Urochordate Betagamma-Crystallin and the Evolutionary Origin of the Vertebrate Eye Lens.
Curr.Biol., 15:1684-, 2005

PubMed Abstract: A refracting lens is a key component of our image-forming camera eye; however, its evolutionary origin is unknown because precursor structures appear absent in nonvertebrates. The vertebrate betagamma-crystallin genes encode abundant structural proteins critical for the function of the lens. We show that the urochordate Ciona intestinalis, which split from the vertebrate lineage before the evolution of the lens, has a single gene coding for a single domain monomeric betagamma-crystallin. The crystal structure of Ciona betagamma-crystallin is very similar to that of a vertebrate betagamma-crystallin domain, except for paired, occupied calcium binding sites. The Ciona betagamma-crystallin is only expressed in the palps and in the otolith, the pigmented sister cell of the light-sensing ocellus. The Ciona betagamma-crystallin promoter region targeted expression to the visual system, including lens, in transgenic Xenopus tadpoles. We conclude that the vertebrate betagamma-crystallins evolved from a single domain protein already expressed in the neuroectoderm of the prevertebrate ancestor. The conservation of the regulatory hierarchy controlling betagamma-crystallin expression between organisms with and without a lens shows that the evolutionary origin of the lens was based on co-option of pre-existing regulatory circuits controlling the expression of a key structural gene in a primitive light-sensing system.

PubMed: 16169492
DOI: 10.1016/J.CUB.2005.08.046

Experimental method

X-RAY DIFFRACTION (1.55 Å)