Glyoxysomal malate dehydrogenase in pumpkin: Cloning of a cDNA and functional analysis of its presequence

作者：Kato A^*; Takeda Yoshikawa Y; Hayashi M; Kondo M; Hara Nishimura I; Nishimura M

来源：Plant and Cell Physiology, 1998, 39(2): 186-195.

• beta-glucuronidase
• malate dehydrogenase (EC 1.1.1.37)
• microbodies
• processing
• pumpkin (Cucurbita sp.)
• targeting signal

Glyoxysomal malate dehydrogenase (gMDH) is an enzyme of the glyoxylate cycle that participates in degradation of storage oil, We have cloned a cDNA for gMDH from etiolated pumpkin cotyledons that encodes a polypeptide consisting of 356 amino acid residues, The nucleotide and N-terminal amino acid sequences revealed that gMDH is synthesized as a precursor with an N-terminal extrapeptide, The N-terminal presequence of 36 amino acid residues contains two regions homologous to those of other microbody proteins, which are also synthesized as large precursors, To investigate the functions of the N-terminal presequence of gMDH, we generated transgenic Arabidopsis that expressed a chimeric protein consisting of beta-glucuronidase and the N-terminal region of gMDH. Immunological and immunocytochemical studies revealed that the chimeric protein was imported into microbodies such as glyoxysomes and leaf peroxisomes and was then subsequently processed, Site-directed mutagenesis studies showed that the conserved amino acids in the N-terminal presequence, Arg-10 and His-17, function as recognition sites for the targeting to plant microbodies, and Cys-36 in the presequence is responsible for its processing. These results correspond to those from the analyses of glyoxysomal citrate synthase (gCS), which was also synthesized as a large precursor, suggesting that common mechanisms that can recognize the targeting or the processing of gMDH and gCS function in higher plant cells.

• 出版日期1998-2