Studies on the structure of rabbit muscle aldolase. Ordering of the tryptic peptides; sequence of 164 amino acid residues in the NH2-terminal BrCN peptide

Structure and expression of mouse aldolase genes. Brain-specific aldolase C amino acid sequence is closely related to aldolase A

Brain-specific aldolase C amino acid sequence (greater than 75% of the coding region) was determined for the first time. Two cDNA clones, pAM1 and pAM2, were identified, from a mouse brain library, by using human aldolase B cDNA as a probe. The larger one, pAM2, identified as a cDNA for aldolase C, has been completely sequenced and covers the 5'-untranslated region of the mRNA and the codons for amino acids 1-227 of the protein. The sequence indicates that aldolase C is more akin to aldolase A than to aldolase B. A cDNA library from mouse muscle was also screened, allowing the identification of clones pAM3 and pAM4, which contain cDNAs for aldolase A. The sequence obtained from pAM3 covers 70% of the coding sequence (amino acids 99-355) from the -COOH part of the protein. The cDNAs for the three aldolases, A, B and C, have been hybridized to RNA from various rat tissues. The results confirm the tissue specificity of the expression of the mRNA for the different isoenzymes and support the hypothesis that aldolase C expression, as aldolase A and B, is regulated at the transcriptional level or, in any case, via mRNA concentration.

Affinity labeling of rabbit muscle fructose-1,6-bisphosphate aldolase with 5'-[p-(fluorosulfonyl)benzoyl]-1,N6-ethenoadenosine

Aldolase contains one tight binding site and one weak binding site per subunit for ATP [Kasprzak, A. and Kochman, M. (1980) Eur. J. Biochem. 104, 443-450]. The reaction of the ATP analog 5'-[p-(fluorosulfonyl)benzoyl]-1,N6-ethenoadenosine with rabbit aldolase A results in linear inactivation of enzyme with respect to covalent linkage of fluorescent label. The enzyme is completely protected against modification in the presence of saturating covalent binding (k2 = 0.033 min-1) is preceded by a fast reversible binding step (Ki = 6.8 mM). Chemical modification of aldolase leads to formation of stable N epsilon (4-carboxybenzenesulfonyl-lysine (Cbs-Lys) and O-(4-carboxybenzenesulfonyl-tyrosine (Cbs-Tyr) derivatives. Almost all Cbs-Lys was found in the N-terminal CNBr peptide (CN-1), whereas Cbs-Tyr was present both in the N-terminal (CN-1) and C-terminal (CN-2) peptide. From carboxypeptidase digestion and tryptic peptide analysis, Cbs-Lys was localized in position 107, a small part of Cbs-Tyr was detected in position 84, and the majority of Cbs-Tyr was found in the C-terminal position Tyr-363. We conclude that the covalent binding of the ATP analog occurs at the mononucleotide tight-binding site of aldolase and is associated with modification of Lys-107 and Tyr-363. This conclusion is based on the measurements of enzymatic activity loss as a function of ATP analog incorporation as well as on previous data. It is postulated that Lys-107, which is the C-6 phosphate binding site for fructose-1,6-P2, is in close proximity to the functionally important Tyr-363. The rather small extent of modification of Tyr-84 (0.15 mol/subunit), is due either to nonspecific protein modification or labeling of the weak mononucleotide binding site.

Isolation and nucleotide sequence of a full-length cDNA coding for aldolase B from human liver

Two recombinant clones, pA2 and pA3, containing cDNA sequences for human aldolase B have been isolated from a full length human liver cDNA library. The larger one, pA3, has been subcloned in M13 phage and completely sequenced with the chain terminator method. The sequence covers 1,600 nucleotides including the whole coding region (1,050 nucleotides), 67 nucleotides from the 5' non-coding region and the whole 3' non-coding region, 440 nucleotides long, down to the poly-A tail. Comparison with rabbit aldolase A and with a partial sequence of rat aldolase B, shows a homology of about 76% for aldolase A and of about 94% for aldolase B, which indicates that the sequenced cDNA codes for the liver isoenzyme. This is the first complete sequence reported for human aldolase B. The pA3 clone strongly hybridizes to 18S mRNA from human adult liver as expected from the size of the isolated cDNA.