Spermine stabilization of folded ribonuclease T1.


Abstract

The interaction of ribonuclease T1 with tetraprotonated spermine (SPM4+), Mg2+, phosphate and other ionic ligands at pH 6.0 was investigated in binding experiments at 25 degrees C and/or by their effects on the midpoint temperature for thermal unfolding of the enzyme. SPM4+ binding with the native protein at 25 degrees C was characterized by an association constant of approximately 2 x 10(4) M-1. This ligand also binds to the unfolded protein but with a approximately 35-fold lower affinity. Phosphate binds at the active site whereas Mg2+ and SPM4+ cations compete for binding at a polyanionic locus that probably involves residues Glu-28, Asp-29, and Glu-31 at the C-terminal end of the alpha-helix. Steady-state kinetic studies using minimal RNA substrates demonstrated that SPM4+ binding with the enzyme does not affect its catalytic activity. SPM4+ also preferentially binds with the folded form of the disulfide-reduced enzyme which has the same or slightly enhanced catalytic properties compared with native ribonuclease T1. The unfolding rate for the native protein in 8 M urea was approximately 8-fold lower in the presence of 0.05 M SPM4+. SPM4+ appears to increase the amplitude of an unobserved fast phase(s) for refolding of the native enzyme. A single kinetic phase characterized refolding of the reduced enzyme which was slightly faster than the slowest refolding phase for the native form. Study holds ProTherm entries: 5173 Extra Details: ionic ligands; association constant; polyanionic locus;,alpha-helix; catalytic properties

Submission Details

ID: iBzycwwB

Submitter: Connie Wang

Submission Date: April 24, 2018, 8:28 p.m.

Version: 1

Publication Details
Walz FG;Kitareewan S,J. Biol. Chem. (1990) Spermine stabilization of folded ribonuclease T1. PMID:1970567
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
1B2M 1998-11-27T00:00:00+0000 2.0 THREE-DIMENSIONAL STRUCTURE OF RIBONULCEASE T1 COMPLEXED WITH AN ISOSTERIC PHOSPHONATE ANALOGUE OF GPU: ALTERNATE SUBSTRATE BINDING MODES AND CATALYSIS.
1BIR 1996-01-04T00:00:00+0000 1.8 RIBONUCLEASE T1, PHE 100 TO ALA MUTANT COMPLEXED WITH 2' GMP
1BU4 1998-09-11T00:00:00+0000 1.9 RIBONUCLEASE 1 COMPLEX WITH 2'GMP
1BVI 1998-09-15T00:00:00+0000 1.9 RIBONUCLEASE T1 (WILDTYPE) COMPLEXED WITH 2'GMP
1CH0 1999-03-30T00:00:00+0000 2.3 RNASE T1 VARIANT WITH ALTERED GUANINE BINDING SEGMENT
1DET 1996-02-20T00:00:00+0000 1.8 RIBONUCLEASE T1 CARBOXYMETHYLATED AT GLU 58 IN COMPLEX WITH 2'GMP
1FYS 2000-10-03T00:00:00+0000 2.0 Ribonuclease T1 V16C mutant
1FZU 2000-10-04T00:00:00+0000 1.8 RNAse T1 V78A mutant
1G02 2000-10-05T00:00:00+0000 1.86 Ribonuclease T1 V16S mutant
1GSP 1997-11-28T00:00:00+0000 2.2 RIBONUCLEASE T1 COMPLEXED WITH 2',3'-CGPS, 1 DAY

Relevant UniProtKB Entries

Percent Identity Matching Chains Protein Accession Entry Name
100.0 Guanyl-specific ribonuclease T1 P00651 RNT1_ASPOR