Determination of the subunit contact region of aspartase.
The subunits of tetrameric enzyme aspartase from Escherichia coli and Pseudomonas fluorescens were incapable of forming hybrid tetramers, suggesting that the subunit contact regions of these two enzymes are not conserved in spite of significant homology between the total sequences of the enzymes. To locate the subunit contact region, we modified cysteine residues of the intermediate species formed during the assembly of the subunits of aspartase from E. coli. Subunits modified with N-ethylmaleimide were unable to assemble into tetramers. Further experiments showed that Cys-88 was the primary residue that was modified. The sequence flanking Cys-88 is quite different from that in the the enzyme from P. fluorescens, suggesting that this region participates in the mutual recognition of subunits.
Yumoto
N
N
Department of Chemistry, Faculty of Science, Kyoto University, Japan.
Murase
S
S
Imaishi
H
H
Tokushige
M
M
D000595:Amino Acid Sequence; D001220:Aspartate Ammonia-Lyase / Q000737:chemistry* / Q000302:isolation & purification / Q000378:metabolism; D002853:Chromatography, Liquid; D004789:Enzyme Activation; D004926:Escherichia coli / Q000201:enzymology; D005033:Ethylmaleimide / Q000737:chemistry; D008969:Molecular Sequence Data; D011551:Pseudomonas fluorescens / Q000201:enzymology; D012689:Sequence Homology, Nucleic Acid
D001220:Aspartate Ammonia-Lyase; D005033:Ethylmaleimide