PENGARUH MUTASI TYROSINE TERHADAP PERUBAHAN ENERGI BEBAS GIBBS PADA PROTEIN FOTOAKTIF KUNING

• Main Authors: , Dian Novitasari, , Dr. Eng. Kuwat Triyana, M.Si.
• Format: Theses and Dissertations NonPeerReviewed
• Published: [Yogyakarta] : Universitas Gadjah Mada 2011
• Subjects: ETD
• Online Access: https://repository.ugm.ac.id/88866/; http://etd.ugm.ac.id/index.php?mod=penelitian_detail&sub=PenelitianDetail&act=view&typ=html&buku_id=50533
• Institution: Universitas Gadjah Mada

Low-barrier hydrogen bond (LBHB) formation on photoactive yellow protein (PYP) has been investigated. Previous X-ray crystallography and neutron crystallography study show that hydrogen bond between the aromatic oxygen of chromophore p-coumaric acid (pCA) and carboxyl hydogen of glutamic acid (E46) was a LBHB. Assuming that proton affinity matching dominates the formation of LBHB, we used tyrosine, instead of pCA, because of similarity of the chemical properties of pCA and tyrosine. Information about protein stability to form the special type of hydrogen bond was analyzed from secondary structure of proteins using circular dichroism (CD) method. Here, we found that value of Gibbs free energy difference of mutant type is lower than the wild-type, 21,70 ± 0,02 kJ/mol and 24 ± 2 kJ/mol for mutant and wild-type in pH balance condition, respectively. These results suggest that mutant is no more stable than the wildtype. The loss of stability for amino acid replacement appears to be due to the loss of hydrogen bonding and unfavorable contacts that account for the destabilization.