The structural basis of the thermostability of SP1, a novel plant (Populus tremula) boiling stable protein

Or Dgany, Ana Gonzalez, Oshrat Sofer, Wangxia Wang, Gennady Zolotnitsky, Amnon Wolf, Yuval Shoham, Arie Altman, Sharon G. Wolf, Oded Shoseyov, Orna Almog

Research output: Contribution to journalArticlepeer-review

72 Scopus citations

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-fliglit 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°C (at pH 7.8). The crystal structure of SP1 was initially determined to 2.4 Å resolution by multi-wave-length anomalous dispersion method from a crystal belonging to the space group 1422. The phases were extended to 1.8 Å 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.

Original languageEnglish
Pages (from-to)51516-51523
Number of pages8
JournalJournal of Biological Chemistry
Volume279
Issue number49
DOIs
StatePublished - Dec 3 2004

ASJC Scopus subject areas

  • Biochemistry
  • Molecular Biology
  • Cell Biology

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