Kretschmar, Michael and Mayr, Eva-Maria and Jaenicke, Rainer (1999) Kinetic and thermodynamic stabilization of the beta gamma-crystallin homolog spherulin 3a from Physarum polycephalum by calcium binding. JOURNAL OF MOLECULAR BIOLOGY, 289 (4). pp. 701-705. ISSN 0022-2836,
Full text not available from this repository. (Request a copy)Abstract
Globular proteins may be stabilized, either intrinsically, at the various levels of the structural hierarchy, or extrinsically, by ligand binding. In the case of the dormant all-beta protein spherulin 3a (S3a) from the slime mold Physarum polycephalum, binding of calcium ions causes extreme kinetic and thermodynamic stabilization. S3a is the only known single-domain member of the two Greek key superfamily of beta gamma-crystallins sharing the extreme long-term stability of its homologs in vertebrate eye lens. Spectral analysis allows two Ca2+-binding sites with K-D = 9 mu M and 200 mu M to be distinguished. Unfolding in the absence and in the presence of Ca2+ gives evidence for extreme kinetic stabilization of the protein: In the absence of Ca2+, the half-time of unfolding in 2.5 M guanidinium chloride (GdmCl) equals 8.3 minutes, whereas in the presence of Ca2+ even in 7.5 M GdmCl, it exceeds nine hours. To reach the equilibrium of unfolding in the absence and in the presence of Ca2+ takes one day and eight weeks, respectively. The corresponding Gibbs free energies (based on the two-state model) are 77 and 135 kJ/mol. Saturation of S3a with Ca2+ leads to an upward shift of the temperature-induced equilibrium transition by ca 20 deg. C. The in situ Ca2+ concentration in the spherules is sufficient for the complete complexation of S3a in vivo. (C) 1999 Academic Press.
| Item Type: | Article |
|---|---|
| Uncontrolled Keywords: | DOMAIN INTERACTIONS; CIRCULAR-DICHROISM; B-CRYSTALLIN; PROTEINS; FOLD; LENS; beta gamma-crystallins; calcium binding; dimer; spherulin; stabilization |
| Subjects: | 500 Science > 570 Life sciences |
| Divisions: | Biology, Preclinical Medicine > Institut für Biophysik und physikalische Biochemie |
| Depositing User: | Dr. Gernot Deinzer |
| Date Deposited: | 01 Feb 2023 09:43 |
| Last Modified: | 01 Feb 2023 09:43 |
| URI: | https://pred.uni-regensburg.de/id/eprint/49167 |
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