Assembly and function of AsGlu2 fibrillar multimer of oat beta-glucosidase.
Oat beta-glucosidase in plastid exists as a long fibrillar structure of AsGlu1 homomultimer (type I) and heteromultimer of AsGlu1 and AsGlu2 (type II). In spite of the high amino acid sequence homology of AsGlu1 and AsGlu2, AsGlu1 assembles into the fibrillar multimers but AsGlu2 forms a dimer when expressed in E. coli. A swapping analysis of AsGlu2 cDNA with AsGlu1 cDNA indicated that the C-terminal segment of AsGlu1 was critical for the fibrillar multimerization. A single substitution of glutamic acid-495 of AsGlu2 in the C-terminal region with lysine, an AsGlu1 counterpart amino acid for the glutamic acid-495, assembled the AsGlu2 into fibrillar homomultimers. The mutant AsGlu2 homomultimer was highly stable and had relatively faster electric mobility in native gel than the AsGlu1 homomultimer. Multimerization increased enzyme affinity to substrates.
Kwak
Su-Nam
SN
Department of Life Science and Biotechnology, College of Natural Science, Kyungpook National University, Daegu 702-701, South Korea.
Kim
Sang-Yeob
SY
Choi
Sa-Ra
SR
Kim
In-Soo
IS
D000595:Amino Acid Sequence; D018554:Avena / Q000201:enzymology*; D007700:Kinetics; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D010940:Plant Proteins / Q000235:genetics; D020836:Protein Structure, Quaternary; D016415:Sequence Alignment; D013379:Substrate Specificity; D001617:beta-Glucosidase / Q000235:genetics / Q000378:metabolism*
D010940:Plant Proteins; D001617:beta-Glucosidase