Swapping functional specificity of a MADS-box protein: Residues
required for Arg80 regulation of arginine metabolism.
Adil Jamai
(1), Evelyne Dubois (1), Andrew K Vershon (2), Francine Messenguy
(1)
(1) Microbiology, Research institute JM Wiame, 1 avenue
E.Gryzon, Brussels 1070, B-1070, Belgium; (2) Department of Molecular
Biology, Waskman Institute of Microbiology, Rutgers University,
Piscataway, New Jersey O8854-8020
Arg80 and Mcm1, two members of the
MADS-box family of DNA-binding proteins, regulate the metabolism of
arginine in association with Arg81, the arginine sensor. In spite of the
high degree of sequence conservation between the MADS-box domains of the
Arg80 and Mcm1 proteins (56 out of 81 aa), these domains are not
interchangeable. To determine which amino acids define the Arg80
specificity, we swapped the amino acids in each secondary structure
element of the Arg80 MADS-box domain with the corresponding amino acids
of Mcm1 and assayed the ability of these chimeras to regulate arginine
metabolic genes in place of the wild type Arg80. The converse experiment
was also performed in which each variant residue in the Mcm1 MADS-box
domain in the context of an Arg80-Mcm1 fusion protein was swapped with
the corresponding residue of Arg80. We show that multiple regions of
Arg80 are important for its function. Interestingly, the residues which
have important roles in determining the specificity of Arg80 are not
those which could contact the DNA but are residues that are likely to be
involved in protein interactions. Many of these residues are clustered
on one side of the protein which could serve as an interface for
interaction with Arg81 or Mcm1. This interface is distinct from the
region of the Mcm1 and human SRF MADS-box proteins used to interact with
their cofactors. It is possible that this alternative interface is used
by other MADS-box proteins to interact with their cofactors.
Return to YGM 2002 Home at SGD