7Z1U

Biochemical implications of the substitution of a unique cysteine residue in sugar beet phytoglobin BvPgb 1.2

Summary for 7Z1U

• Entry DOI: 10.2210/pdb7z1u/pdb
• Descriptor: Non-symbiotic hemoglobin class 1, PROTOPORPHYRIN IX CONTAINING FE (3 entities in total)
• Functional Keywords: phytoglobin, globin fold, redox balance, cysteine substitution, oxygen binding
• Biological source: Beta vulgaris
• Total number of polymer chains: 2
• Total formula weight: 39675.45

Authors

Nyblom, M.,Christensen, S.,Leiva Eriksson, N.,Bulow, L. (deposition date: 2022-02-25, release date: 2022-09-07, Last modification date: 2024-01-31)

Primary citation

Christensen, S.,Groth, L.,Leiva-Eriksson, N.,Nyblom, M.,Bulow, L.
Oxidative Implications of Substituting a Conserved Cysteine Residue in Sugar Beet Phytoglobin BvPgb 1.2.
Antioxidants, 11:-, 2022

PubMed Abstract: Phytoglobins (Pgbs) are plant-originating heme proteins of the globin superfamily with varying degrees of hexacoordination. Pgbs have a conserved cysteine residue, the role of which is poorly understood. In this paper, we investigated the functional and structural role of cysteine in BvPgb1.2, a Class 1 Pgb from sugar beet (), by constructing an alanine-substituted mutant (Cys86Ala). The substitution had little impact on structure, dimerization, and heme loss as determined by X-ray crystallography, size-exclusion chromatography, and an apomyoglobin-based heme-loss assay, respectively. The substitution significantly affected other important biochemical properties. The autoxidation rate increased 16.7- and 14.4-fold for the mutant versus the native protein at 25 °C and 37 °C, respectively. Thermal stability similarly increased for the mutant by ~2.5 °C as measured by nano-differential scanning fluorimetry. Monitoring peroxidase activity over 7 days showed a 60% activity decrease in the native protein, from 33.7 to 20.2 U/mg protein. When comparing the two proteins, the mutant displayed a remarkable enzymatic stability as activity remained relatively constant throughout, albeit at a lower level, ~12 U/mg protein. This suggests that cysteine plays an important role in BvPgb1.2 function and stability, despite having seemingly little effect on its tertiary and quaternary structure.

PubMed: 36009334
DOI: 10.3390/antiox11081615

Experimental method

X-RAY DIFFRACTION (2.24 Å)