Different unfolding pathways for mesophilic and thermophilic homologues of serine hydroxymethyltransferase.


To determine how much information can be transferred from folding and unfolding studies of one protein to another member of the same family or between the mesophilic and thermophilic homologues of a protein, we have characterized the equilibrium unfolding process of the dimeric enzyme serine hydroxymethyltransferase (SHMT) from two sources, Bacillus subtilis (bsSHMT) and Bacillus stearothermophilus (bstSHMT). Although the sequences of the two enzymes are highly identical ( approximately 77%) and homologous (89%), bstSHMT shows a significantly higher stability against both thermal and urea denaturation than bsSHMT. The GdmCl-induced unfolding of bsSHMT was found to be a two-step process with dissociation of the native dimer, resulting in stabilization of a monomeric species, followed by the unfolding of the monomeric species. A similar unfolding pathway has been reported for Escherichia coli aspartate aminotransferase, a member of the type I fold family of PLP binding enzymes such as SHMT, the sequence of which is only slightly identical ( approximately 14%) with that of SHMT. In contrast, for bstSHMT, a highly cooperative unfolding without stabilization of any monomeric intermediate was observed. These studies suggest that mesophilic proteins of the same structural family even sharing a low level of sequence identity may follow a common unfolding mechanism, whereas the mesophilic and thermophilic homologues of the same protein despite having a high degree of sequence identity may follow significantly different unfolding mechanisms. Study holds ProTherm entries: 15604, 15605, 15606, 15607 Extra Details: Transition 1 dimeric enzyme; two-step process; monomeric intermediate; thermophilic

Submission Details

ID: bq6EHSBs3

Submitter: Connie Wang

Submission Date: April 24, 2018, 8:46 p.m.

Version: 1

Publication Details
Bhatt AN;Prakash K;Subramanya HS;Bhakuni V,Biochemistry (2002) Different unfolding pathways for mesophilic and thermophilic homologues of serine hydroxymethyltransferase. PMID:12356312
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 UniProtKB Entries

Percent Identity Matching Chains Protein Accession Entry Name
100.0 Serine hydroxymethyltransferase P39148 GLYA_BACSU
95.4 Serine hydroxymethyltransferase A7Z9Q9 GLYA_BACVZ
91.1 Serine hydroxymethyltransferase Q65DW5 GLYA_BACLD
96.8 Serine hydroxymethyltransferase Q5KUI2 GLYA_GEOKA
93.8 Serine hydroxymethyltransferase A4ITJ9 GLYA_GEOTN