Latherin: a surfactant protein of horse sweat and saliva

McDonald, R.E., Fleming, R.I., Beeley, J.G., Bovell, D.L., Lu, J.R., Zhao, X., Cooper, A. and Kennedy, M.W. (2009) Latherin: a surfactant protein of horse sweat and saliva. PLoS ONE, 4(5), e5726-.. (doi: 10.1371/journal.pone.0005726)

Abstract

Horses are unusual in producing protein-rich sweat for thermoregulation, a major component of which is latherin, a highly surface-active, non-glycosylated protein. The amino acid sequence of latherin, determined from cDNA analysis, is highly conserved across four geographically dispersed equid species (horse, zebra, onager, ass), and is similar to a family of proteins only found previously in the oral cavity and associated tissues of mammals. Latherin produces a significant reduction in water surface tension at low concentrations (=1 mg ml-1), and therefore probably acts as a wetting agent to facilitate evaporative cooling through a waterproofed pelt. Neutron reflection experiments indicate that this detergent-like activity is associated with the formation of a dense protein layer, about 10 � thick, at the air-water interface. However, biophysical characterization (circular dichroism, differential scanning calorimetry) in solution shows that latherin behaves like a typical globular protein, although with unusual intrinsic fluorescence characteristics, suggesting that significant conformational change or unfolding of the protein is required for assembly of the air-water interfacial layer. RT-PCR screening revealed latherin transcripts in horse skin and salivary gland but in no other tissues. Recombinant latherin produced in bacteria was also found to be the target of IgE antibody from horse-allergic subjects. Equids therefore may have adapted an oral/salivary mucosal protein for two purposes peculiar to their lifestyle, namely their need for rapid and efficient heat dissipation and their specialisation for masticating and processing large quantities of dry food material.

• Item Type: Articles
• Additional Information: This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
• Status: Published
• Refereed: Yes
• Glasgow Author(s) Enlighten ID: Kennedy, Professor Malcolm and McDonald, Dr Rhona and Cooper, Professor Alan
• Authors: McDonald, R.E., Fleming, R.I., Beeley, J.G., Bovell, D.L., Lu, J.R., Zhao, X., Cooper, A., and Kennedy, M.W.
• Subjects: Q Science > QP Physiology; Q Science > QH Natural history > QH301 Biology
• College/School: College of Science and Engineering > School of Chemistry; College of Medical Veterinary and Life Sciences > School of Life Sciences
• Journal Name: PLoS ONE
• Publisher: Public Library of Science
• ISSN: 1932-6203
• ISSN (Online): 1932-6203
• Published Online: 29 May 2009
• Copyright Holders: Copyright © 2009 The Authors
• First Published: First published in PLoS ONE 2009 4(5): e5726
• Publisher Policy: Reproduced in accordance with the copyright policy of the publisher

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