The conserved histidine 106 of large thioredoxin reductases is likely to have a structural role but not a base catalyst function.
FEBS Lett
; 579(3): 745-8, 2005 Jan 31.
Article
in En
| MEDLINE
| ID: mdl-15670839
ABSTRACT
The catalytic activity of selenocysteine-containing thioredoxin reductases can be mimicked by cysteine-variants if the local environment at the C-terminal redox center supports thiol activation. This concept of a linear catalytic site was challenged by structural data suggesting that the invariant residue His106 functions as a base catalyst for the dithiol-disulphide exchange reaction between enzyme and substrate. As reported here, we changed His106 to asparagine, glutamine, and phenylalanine in various C-terminal mutants of Drosophila melanogaster thioredoxin reductase. The catalytic activity dropped considerably, yet pH-profiles did not reveal differences, rendering a function for His106 as a base catalyst unlikely. Interestingly, the phenylalanine-mutants, designed as negative controls were the most active mutants which suggests rather a structural role of His106.
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Collection:
01-internacional
Database:
MEDLINE
Main subject:
Thioredoxin-Disulfide Reductase
/
Histidine
Limits:
Animals
Language:
En
Journal:
FEBS Lett
Year:
2005
Type:
Article
Affiliation country:
Germany