Cloning and expression of novel isoforms of 6‐phosphofructo‐2‐kinase/fructose‐2,6‐bisphosphatase from bovine heart

Abstract

Distinct 6‐phosphofructo‐2‐kinase (PFK‐2)/fructose 2,6‐bisphosphatase (FBPase‐2) cDNAs were cloned from bovine heart, showing that PFK‐2/FBPase‐2 gene B, which contains 16 exons, codes for at least five mRNAs. Three of them (B1, B2, B4) could encode the 58,000‐M r isozyme. In B2 mRNA, exon 15 encodes four more residues than in Bl. In B4 mRNA, exon 15 encodes six more residues than in B1, butexon 16 (20 residues) is missing. B3 mRNA corresponds to the 54,000‐M r isozyme. It lacks exon 15 and also differs from the other mRNAs in the 5' noncoding region. B5 mRNA encodes a truncated form. When expressed in E. coli, the recombinant isoforms corresponding to all these mRNAs except B5 exhibited PFK‐2 activity.

Molecular cloning and tissue‐specific expression of mouse kidney 6‐phosphofructo‐2‐kinase/fructose‐2,6‐bisphosphatase

“…The detection of multiple bands in Northern blots probed with the heart-type clone 2kbC5 is consistent with the identification of at least five mRNAs derived from gene B [28]. The entire PFK-2/FBPase-2 heart-type transcript predicted to correspond to 2kbC5 (due to its intense signal in kidney) detected on the Northern blot appeared to be approx.…”

“…The differential splicing implied by this result is supported by earlier characterization of the homologous bovine autosomal locus which has been shown to encode at least five mRNAs [28]. Comparison of the mouse heart-type isozyme encoded by 2kbC5 with --9 Fig.…”

“…Potential phosphorylation sites are underlined: two sites for cAMP-dependent protein kinase (PKA) at Ser-469 and Ser-486 and a protein kinase C (PKC) phosphorylation site at Thr-478. These sites correspond to regulatory sites previously characterized in rat and bovine heart-type isozymes [11,26,28]. Exon prediction is based on homology to rat heart genomic sequence [11].…”

Transcriptional control of genes that regulate glycolysis and gluconeogenesis in adult liver

“…The best characterized are the liver (L), skeletal muscle (M), heart (H), testis (T) and brain isoenzymes. The sequence of the L mRNA of several species is known [30][31][32] as well as that of the rat M-, T-and H-type mRNAs [33][34][35][36]. In addition, a fetal (F)-type mRNA was recently identified [37].…”

Phosphorylation and Activation of Heart 6-Phosphofructo-2-kinase by Protein Kinase B and Other Protein Kinases of the Insulin Signaling Cascades

“…Peptide sequence analysis revealed that the M r 54,000 form lacks phosphorylation sites for PKA (Ser-466 and Ser-483) and protein kinase C (Ser-466 and Thr-475), which are encoded by exon 15 and thus present in the M r 58,000 form (15,17). The situation in bovine heart is further complicated by the fact that four different mRNAs have been characterized (18). One (B3) lacks exon 15 and is therefore similar to the M r 54,000 form.…”