Biology:Chromoprotein
A chromoprotein is a conjugated protein that contains a pigmented prosthetic group (or cofactor). A common example is haemoglobin, which contains a heme cofactor, which is the iron-containing molecule that makes oxygenated blood appear red. Other examples of chromoproteins include other hemochromes, cytochromes, phytochromes and flavoproteins.[1]
In hemoglobin there exists a chromoprotein (tetramer MW:4 x 16.125 =64.500), namely heme, consisting of Fe++ four pyrrol rings.
A single chromoprotein can act as both a phytochrome and a phototropin due to the presence and processing of multiple chromophores. Phytochrome in ferns contains PHY3 which contains an unusual photoreceptor with a dual-channel possessing both phytochrome (red-light sensing) and phototropin (blue-light sensing) and this helps the growth of fern plants at low sunlight.[2]
The GFP protein family includes both fluorescent proteins and non-fluorescent chromoproteins. Through mutagenesis or irradiation, the non-fluorescent chromoproteins can be converted to fluorescent chromoproteins.[3] An example of such converted chromoprotein is "kindling fluorescent proteins" or KFP1 which was converted from a mutated non-fluorescent Anemonia sulcata chromoprotein to a fluorescent chromoprotein.[4]
Sea anemones contain purple chromoprotein shCP with its GFP-like chromophore in the trans-conformation. The chromophore is derived from Glu-63, Tyr-64 and Gly-65 and the phenolic group of Tyr-64 plays a vital role in the formation of a conjugated system with the imidazolidone moiety resulting a high absorbance in the absorption spectrum of chromoprotein in the excited state. The replacement of Tyrosine with other amino acids leads to the alteration of optical and non-planer properties of the chromoprotein. Fluorescent proteins such as anthrozoa chromoproteins emit long wavelengths [4]
14 chromoproteins were engineered to be expressed in E. coli for synthetic biology.[5] However, chromoproteins bring high toxicities to their E. coli hosts, resulting in the loss of colors. mRFP1, the monomeric red fluorescent protein,[6] which also displays distinguishable color under ambient light, was found to be less toxic.[7] Color-changing mutagenesis on amino acids 64–65 of the mRFP1 fluorophore was done to acquire different colors.
References
- ↑ An Introduction to Biochemistry. Elsevier. 1940. p. 131. ISBN 9781483225395. https://books.google.com/books?id=YkOaBQAAQBAJ&pg=PA131.
- ↑ "A single chromoprotein with triple chromophores acts as both a phytochrome and a phototropin". Proceedings of the National Academy of Sciences of the United States of America 103 (47): 17997–18001. November 2006. doi:10.1073/pnas.0603569103. PMID 17093054. Bibcode: 2006PNAS..10317997K.
- ↑ "Traditional GFP-type cyclization and unexpected fragmentation site in a purple chromoprotein from Anemonia sulcata, asFP595". Biochemistry 43 (42): 13598–13603. October 2004. doi:10.1021/bi0488247. PMID 15491166.
- ↑ 4.0 4.1 "Crystal structure of the blue fluorescent protein with a Leu-Leu-Gly tri-peptide chromophore derived from the purple chromoprotein of Stichodactyla haddoni". International Journal of Biological Macromolecules 130: 675–684. June 2019. doi:10.1016/j.ijbiomac.2019.02.138. PMID 30836182.
- ↑ "Engineering a palette of eukaryotic chromoproteins for bacterial synthetic biology". Journal of Biological Engineering 12 (1): 8. 2018-05-10. doi:10.1186/s13036-018-0100-0. PMID 29760772.
- ↑ "A monomeric red fluorescent protein". Proceedings of the National Academy of Sciences of the United States of America 99 (12): 7877–82. June 2002. doi:10.1073/pnas.082243699. PMID 12060735. Bibcode: 2002PNAS...99.7877C.
- ↑ "Overcoming chromoprotein limitations by engineering a red fluorescent protein". Analytical Biochemistry 611: 113936. December 2020. doi:10.1016/j.ab.2020.113936. PMID 32891596.
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