Functional comparison of the NAD binding cleft of ADP-ribosylating toxins

Biochemistry
K M DolanJoan C Olson

Abstract

Although a common core structure forms the active site of ADP-ribosylating (ADPRT) toxins, the limited-sequence homology within this region suggests that different mechanisms are being used by toxins to perform their shared function. To explain differences in their mechanisms of NAD binding and hydrolysis, the functional interrelationship of residues predicted to perform similar functions in the beta3-strand of the NAD binding cleft of different ADPRT toxins was compared. Replacing Tyr54 in the A-subunit of diphtheria toxin (DTA) with a serine, its functional homologue in cholera toxin (CT), resulted in the loss of catalytic function but not NAD binding. The catalytic role of the aromatic portion of Tyr54 in the ADPRT reaction was confirmed by the ability of a Tyr54-to-phenylalanine DTA mutant to retain ADPRT activity. In reciprocal studies, positioning a tyrosine in the beta3-strand of the A1-subunit of CT (CTA1) caused both loss of function and altered structure. The restricted flexibility of the CTA1 active site relative to function became evident upon the loss of ADPRT activity when a conservative Val60-to-leucine mutation was performed. We conclude from our studies that DT and CT maintain a similar mechanism of NAD binding...Continue Reading

References

Aug 23, 2005·Infection and Immunity·Claudia L RochaJoan C Olson
Feb 7, 2002·Biochemical and Biophysical Research Communications·Jennifer E FraylickJoan C Olson
Sep 8, 2006·The FEBS Journal·Kenneth P HolbournK Ravi Acharya
Jan 13, 2006·Trends in Biochemical Sciences·Susan P YatesA Rod Merrill
Jan 1, 2004·Chemistry & Biology·Oleg KurnasovTadhg P Begley
Nov 6, 2013·Proceedings of the National Academy of Sciences of the United States of America·Jee-Hyun KimDirk Schnappinger
Aug 23, 2003·The Journal of Biological Chemistry·Hazel R EvansK Ravi Acharya

Related Concepts

PARP1
Proteins, Recombinant DNA
Mutagenesis, Site-Directed
Procholeragenoid
Homologous Sequences, Amino Acid
NADH
Protein Conformation
Poly(ADP-ribose) Polymerases
Endorphenyl
Serine

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