Cloning, cDNA analysis and prolactin-dependent expression of a marsupial alpha-lactalbumin

Abstract

The gene for alpha-lactalbumin has been cloned from a tammar wallaby (Macropus eugenii) mammary gland cDNA library. Tammar alpha-lactalbumin has approximately 50 and 30% homology to the alpha-lactalbumins of eutherians at the levels of nucleotide and protein sequence respectively. Comparison of the inferred tammar polypeptide sequence with the sequence of the eutherian proteins reveals extensive divergence at almost all of the non-essential amino acid residues. However, the hydropathy plots of the tammar protein are almost identical to those of eutherian alpha-lactalbumins, suggesting that protein conformation is conserved. The tammar gene encodes a transcript of approximately 975 bases. Northern blot analysis of hormone-stimulated mammary gland explants shows that maximal induction of alpha-lactalbumin mRNA is dependent on prolactin and that expression is not modulated by other hormones that play a role in the initiation of lactation in eutherians.

A marsupial β-lactoglobulin gene: characterization and prolactin-dependent expression

“…The prolactin-dependent induction of tammar ß-lactoglobulin is similar to the previous findings for the maximal in-vitro induction of tx-lactalbumin (Nicholas & Tyndale-Biscoe, 1985;Collet et al 1990) and a 19 kDa casein (Maher & Nicholas, 1987) in this species. The in-vitro hormonal regulation of tammar ß-lactoglobulin synthesis appears to share some similarity with that seen in vitro for sheep (Puissant et al 1990).…”

“…In the rabbit, induction of milk protein synthesis can occur in the presence of prolactin alone but maximal synthesis is dependent on the addition of insulin and cortisol to the media (Devinoy, Houdebine & Delouis, 1978;Devinoy et al 1988). In contrast, the maximal induction of 0C-lactalbumin and a 19 kDa casein in mammary gland expiants from the pregnant tammar wallaby (Macropus eugenii) appears to be dependent on prolactin alone and independent of other hormones known to play a role in the induction of milk protein synthesis in eutherians (Nicholas & Tyndale-Biscoe, 1985;Maher & Nicholas, 1987;Collet, Joseph & Nicholas, 1990). The hormone-dependent stimulation of ß-lactoglobulin gene expression in mammary gland expiants has recently been reported for the sheep (Puissant, Attal & Houdebine, 1990).…”

Models of the three-dimensional structures of echidna, horse, and pigeon lysozymes: Calcium-binding lysozymes and their relationship with α-lactalbumins

“…These major changes were accommodated in the echidna milk lysozyme-I model with minimal disruption of the 'archetypal' lysozyme structure. The termination of the polypeptide chain of echidna milk lysozyme-I is at Cys 127 (hen eggwhite lysozyme numbering), a feature that is at present shared only with pigeon eggwhite lysozyme and the 0~-lactalbumins of the marsupials Macropus rufogriseus (red-necked wallaby) and Macropus eugenii (tammar wallaby) (Collet et al, 1990) and the monotreme Ornithorhyncus anatinus (platypus) (Shaw et al, 1993).…”

Higher female than male recombination rates in a marsupial mammal, the tammar wallaby (<i>Macropus eugenii</i>)

“…T he probes used were pB862. pB 1211, pB72, and pB65, which contain LLP (Collet et al, 1989), LALBA (Collet et al, 1990), …”