Equilibrium unfolding of the C-terminal SAM domain of p73.


The sterile alpha motif (SAM) domain is a protein module of approximately 65 to 70 amino acids found in many diverse proteins whose functions range from signal transduction to transcriptional repression. The alpha splice variant of p73 (p73 alpha), a homologue of the tumor suppressor p53, has close to its C-terminus a SAM motif. Here, we report the folding equilibrium properties of the p73 alpha SAM domain (SAMp73) by using different biophysical techniques (circular dichroism, fluorescence, and Fourier transform infrared spectroscopies, and differential scanning calorimetry). Those probes indicate that SAMp73 folds via a two-state mechanism. Fluorescence experiments performed at different pHs showed two titrations: the first one due to an acid residue (with a pK(a) = 4.5 +/- 0.3) and the second due to deprotonation of tyrosine residues. The conformational stability of the protein upon chemical denaturation was determined over the pH range 3 to 10. The maximum conformational stability is DeltaG = 5.7 +/- 0.4 kcal x mol(-1) (at 25 degrees C) and occurs in a broad maximum, with little variation, between pH 6 and 10. The high melting temperature of SAMp73 (T(m) = 93.5 degrees C), despite its moderate conformational stability at 25 degrees C, can be ascribed to its low heat capacity change upon unfolding, DeltaC(p), which is estimated to be around 915 cal x K(-1) x mol(-1) at 25 degrees C and only around 543 cal x K(-1) x mol(-1) at the T(m). The implications of the temperature-dependent nature of DeltaC(p) are discussed in relation to the thermal stability of proteins as opposed to their conformational stability at room temperature. Study holds ProTherm entries: 14944, 14945 Extra Details: C-terminal of sterile alpha motif domain sterile alpha motif; two-state mechanism; conformational stability

Submission Details

ID: 6cgtNP8Q4

Submitter: Connie Wang

Submission Date: April 24, 2018, 8:45 p.m.

Version: 1

Publication Details
Barrera FN;Garzón MT;Gómez J;Neira JL,Biochemistry (2002) Equilibrium unfolding of the C-terminal SAM domain of p73. PMID:11980478
Additional Information

Structure view and single mutant data analysis

Study data

No weblogo for data of varying length.
Colors: D E R H K S T N Q A V I L M F Y W C G P

Data Distribution

Studies with similar sequences (approximate matches)

Correlation with other assays (exact sequence matches)

Relevant PDB Entries

Structure ID Release Date Resolution Structure Title
1COK 1999-05-28T00:00:00+0000 0 STRUCTURE OF THE C-TERMINAL DOMAIN OF P73
1DXS 2000-01-15T00:00:00+0000 2.54 Crystal structure of the C-terminal sterile alpha motif (SAM) domain of human p73 alpha splice variant
2KBY 2008-12-12T00:00:00+0000 0 The Tetramerization Domain of Human p73
2MPS 2014-06-02T00:00:00+0000 0 Structure of complex of MDM2(3-109) and P73 TAD(10-25)
2NB1 2016-01-19T00:00:00+0000 0 P63/p73 hetero-tetramerisation domain
2WQI 2009-08-21T00:00:00+0000 1.7 Crystal structure of the human p73 tetramerization domain
2WQJ 2009-08-21T00:00:00+0000 2.0 Crystal structure of a truncated variant of the human p73 tetramerization domain
2WTT 2009-09-21T00:00:00+0000 2.3 Structure of the human p73 tetramerization domain (crystal form II)
2XWC 2010-11-03T00:00:00+0000 1.82 Crystal structure of the DNA binding domain of human TP73 refined at 1.8 A resolution
3VD0 2012-01-04T00:00:00+0000 2.95 structure of p73 DNA binding domain tetramer modulates p73 transactivation

Relevant UniProtKB Entries

Percent Identity Matching Chains Protein Accession Entry Name
94.0 Tumor protein p73 Q9JJP2 P73_MOUSE
100.0 Tumor protein p73 O15350 P73_HUMAN
100.0 Tumor protein p73 Q9XSK8 P73_CHLAE