University Of Tasmania
Enjapoori et al. 2014 Monotreme Lactation Protein is highly expressed in monotreme milk Genome Biol Evol.pdf (1.87 MB)

Monotreme lactation protein Is highly expressed in monotreme milk and provides antimicrobial protection

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journal contribution
posted on 2023-05-18, 07:08 authored by Enjapoori, AK, Grant, TR, Stewart NicolStewart Nicol, Lefevre, CM, Nicholas, KR, Sharp, JA
Monotremes (platypus and echidna) are the descendants of the oldest ancestor of all extant mammals distinguished from other mammals by mode of reproduction. Monotremes lay eggs following a short gestation period and after an even briefer incubation period, altricial hatchlings are nourished over a long lactation period with milk secreted by nipple-less mammary patches located on the female’s abdomen. Milk is the sole source of nutrition and immune protection for the developing young until weaning. Using transcriptome and mass spectrometry analysis of milk cells and milk proteins, respectively, a novel Monotreme Lactation Protein (MLP) was identified as a major secreted protein in milk. We show that platypus and short-beaked echidna MLP genes show significant homology and are unique to monotremes. The MLP transcript was shown to be expressed in a variety of tissues; however, highest expression was observed in milk cells and was expressed constitutively from early to late lactation. Analysis of recombinant MLP showed that it is an N-linked glycosylated protein and biophysical studies predicted that MLP is an amphipathic, α-helical protein, a typical feature of antimicrobial proteins. Functional analysis revealed MLP antibacterial activity against both opportunistic pathogenic Staphylococcus aureus and commensal Enterococcus faecalis bacteria but showed no effect on Escherichia coli, Pseudomonas aeruginosa, Staphylococcus epidermidis, and Salmonella enterica. Our data suggest that MLP is an evolutionarily ancient component of milk-mediated innate immunity absent in other mammals. We propose that MLP evolved specifically in the monotreme lineage supporting the evolution of lactation in these species to provide bacterial protection, at a time when mammals lacked nipples.


National Geographic Society


Publication title

Genome Biology and Evolution










School of Natural Sciences


Oxford University Press

Place of publication

Oxford, UK

Rights statement

? Copyright The Author(s) 2014

Repository Status

  • Open

Socio-economic Objectives

Expanding knowledge in the environmental sciences

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