Molecular basis of impaired pyruvate kinase isozyme conversion in erythroid cells: a single amino acid substitution near the active site and decreased mRNA content of the R-type PK.
Conversion of pyruvate kinase (PK) isozymes from M2- to R-PK has been observed during erythroid cell maturation. To understand this mechanism, we analyzed the PK gene of a R-PK deficient patient, in whose erythrocytes the M2-PK was persistently expressed. A point mutation, 1102 GTC-->TTC was identified in the R-PK cDNA, and it caused a single amino acid substitution from 368Val-->Phe. The residue is very close to the 372nd Gln, the putative binding site of the monovalent cation (K+). The impaired K+ binding would cause the decreased affinity for phosphoenolpyruvate, consequently the variant PK may be extremely unstable. Although the proband's other PK allele did not have any structural change, the R-PK mRNA level in reticulocytes was decreased. These findings suggested that both the structural mutation near the active site and the decreased mRNA level of the R-PK were responsible for the disorder.
Kanno
H
H
Okinaka Memorial Institute for Medical Research, Tokyo, Japan.
Fujii
H
H
Tsujino
G
G
Miwa
S
S
D000595:Amino Acid Sequence; D000596:Amino Acids / Q000235:genetics*; D001483:Base Sequence; D001665:Binding Sites; D002478:Cells, Cultured; D004247:DNA; D004912:Erythrocytes / Q000201:enzymology*; D006801:Humans; D007527:Isoenzymes / Q000235:genetics* / Q000378:metabolism; D008969:Molecular Sequence Data; D017354:Point Mutation; D011770:Pyruvate Kinase / Q000172:deficiency / Q000235:genetics* / Q000378:metabolism; D012333:RNA, Messenger / Q000378:metabolism*; D013329:Structure-Activity Relationship
D000596:Amino Acids; D007527:Isoenzymes; D012333:RNA, Messenger; D004247:DNA; D011770:Pyruvate Kinase