research Categories: >> Structure and Function of AURAcyanins:
Structure and Function of Auracyanins
First reported in 1988 by the Blankenship group, auracyanins represent a class of small blue copper proteins. Presently, they are only found in the photosynthetic bacterium Chloroflexus aurantiacus, which produces two distinct but closely related forms: Auracyanin A and Auracyanin B. Based on their redox potentials, their similarity to other cupredoxins, and the lack of any iron-based soluble electron carriers in C. aurantiacus, auracyanins most likely function as electron carriers in the periplasmic electron-transfer step of photosynthesis. Recently, two cytochrome-containing complexes from C. aurantiacus are found to be members of a new class of bacterial membrane oxidoreductases, and are candidates for electron donors to auracyanins. The significance of two forms of auracyanins in C. aurantiacus is currently under investigation. A 1.55? crystal structure of auracyanin B has been resolved, while the structure of A is well under way. The genes for both proteins have been cloned in bacterial expression systems allowing overexpression of large quantities of proteins for further biochemical studies. We measure protein expression levels using western blots employing antibodies specific for either auracyanin A or B, as well as quantitative real-time RT-PCR of auracyanin mRNAs. We also study the copper active sites using uv-vis, electron paramagnetic and x-ray absorption spectroscopy. A new twist in our studies is the report that azurin, a closely related cupredoxin, has been shown to enter human cancer cells and induce apoptosis. Experiments are currently being done to see whether or not auracyanins would have a similar effect.
Selected Publications
1. Trost, J. T., J. D. McManus, et al. (1988). "Auracyanin, a Blue Copper Protein from the Green Photosynthetic Bacterium Chloroflexus-Aurantiacus." Biochem27(20): 7858-7863.
2. McManus, J. D., D. C. Brune, et al. (1992). "Isolation, characterization, and amino acid sequences of auracyanins, blue copper proteins from the green photosynthetic bacterium Chloroflexus aurantiacus." J Biol Chem267(10): 6531-40.
3. Bond, C. S., R. E. Blankenship, H.C. Freeman, J.M. Guss, M.J. Maher, F.M. Selvaraj, M.C.J. Wilce, and K.M. Willingham. (2001). " Crystal structure of auracyanin, a "blue" copper protein from the green thermophilic photosynthetic bacterium Chloroflexus aurantiacus." J Mol Biol306(1): 47-67.
4. Yanyushin, M. F. (2002). "Fractionation of cytochromes of phototrophically grown Chloroflexus aurantiacus. Is there a cytochrome bc complex among them?" FEBS Letters512(1-3): 125-128.
5. Yamada, T., M. Goto, V. Punj, O. Zaborina, M.L. Chen, K. Kimbara, D. Majumdar, E. Cunningham, T.K. Das Gupta, and A.M. Chakrabarty. (2002) "Bacterial redox protein azurin, tumor suppressor protein p53, and regression of cancer. PNAS99(22): 14098-14103.