1SI9

Boiling stable protein isolated from Populus tremula

Summary for 1SI9

• Entry DOI: 10.2210/pdb1si9/pdb
• Descriptor: stable protein 1, GLYCEROL (3 entities in total)
• Functional Keywords: stress, heat shock responsive, boiling-soluble, plant protein
• Biological source: Populus tremula
• Total number of polymer chains: 3
• Total formula weight: 37545.17

Authors

Almog, O.,Gonzales, A.,Shoseyov, O.,Dgany, O.,Sofer, O.,Wolf, S.G. (deposition date: 2004-02-29, release date: 2004-09-21, Last modification date: 2024-02-14)

Primary citation

Dgany, O.,Gonzalez, A.,Sofer, O.,Wang, W.,Zolotnitsky, G.,Wolf, A.,Shoham, Y.,Altman, A.,Wolf, S.G.,Shoseyov, O.,Almog, O.
The Structural Basis of the Thermostability of SP1, a Novel Plant (Populus tremula) Boiling Stable Protein.
J.Biol.Chem., 279:51516-51523, 2004

PubMed Abstract: We previously reported on a new boiling stable protein isolated from aspen plants (Populus tremula), which we named SP1. SP1 is a stress-related protein with no significant sequence homology to other stress-related proteins. It is a 108-amino-acid hydrophilic polypeptide with a molecular mass of 12.4 kDa (Wang, W. X., Pelah, D., Alergand, T., Shoseyov, O., and Altman, A. (2002) Plant Physiol. 130, 865-875) and is found in an oligomeric form. Preliminary electron microscopy studies and matrix-assisted laser desorption ionization time-of-flight mass spectrometry experiments showed that SP1 is a dodecamer composed of two stacking hexamers. We performed a SDS-PAGE analysis, a differential scanning calorimetric study, and crystal structure determination to further characterize SP1. SDS-PAGE indicated a spontaneous assembly of SP1 to one stable oligomeric form, a dodecamer. Differential scanning calorimetric showed that SP1 has high thermostability i.e. Tm of 107 degrees C (at pH 7.8). The crystal structure of SP1 was initially determined to 2.4 A resolution by multi-wavelength anomalous dispersion method from a crystal belonging to the space group I422. The phases were extended to 1.8 A resolution using data from a different crystal form (P21). The final refined molecule includes 106 of the 108 residues and 132 water molecules (on average for each chain). The R-free is 20.1%. The crystal structure indicated that the SP1 molecule has a ferredoxin-like fold. Strong interactions between each two molecules create a stable dimer. Six dimers associate to form a ring-like-shaped dodecamer strongly resembling the particle visualized in the electron microscopy studies. No structural similarity was found between the crystal structure of SP1 and the crystal structure of other stress-related proteins such as small heat shock proteins, whose structure has been already determined. This structural study further supports our previous report that SP1 may represent a new family of stress-related proteins with high thermostability and oligomerization.

PubMed: 15371455
DOI: 10.1074/jbc.M409952200

Experimental method

X-RAY DIFFRACTION (2.27 Å)