Journal article
Functional diversification and evolution of antifreeze proteins in the antarctic fish Lycodichthys dearborni
Journal of molecular evolution, Vol.71(2), pp.111-118
08/2010
Handle:
https://hdl.handle.net/2376/103816
PMID: 20686757
Abstract
Antifreeze proteins (AFPs) have independently evolved in many organisms. AFPs act by binding to ice crystals, effectively lowering the freezing point. AFPs are often at high copy number in a genome and diversity exists between copies. Type III antifreeze proteins are found in Arctic and Antarctic eel pouts, and have previously been shown to evolve under positive selection. Here we combine molecular and proteomic techniques to understand the molecular evolution and diversity of Type III antifreeze proteins in a single individual Antarctic fish Lycodichthys dearborni. Our expressed sequence tag (EST) screen reveals that at least seven different AFP variants are transcribed, which are ultimately translated into five different protein isoforms. The isoforms have identical 66 base pair signal sequences and different numbers of subsequent ice-binding domains followed by a stop codon. Isoforms with one ice-binding unit (monomer), two units (dimer), and multiple units (multimer) were present in the EST library. We identify a previously uncharacterized protein dimer, providing further evidence that there is diversity between Type III AFP isoforms, perhaps driven by positive selection for greater thermal hysteresis. Proteomic analysis confirms that several of these isoforms are translated and present in the liver. Our molecular evolution study shows that paralogs have diverged under positive selection. We hypothesize that antifreeze protein diversity is an important contributor to depressing the serum freezing point.
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Details
- Title
- Functional diversification and evolution of antifreeze proteins in the antarctic fish Lycodichthys dearborni
- Creators
- Joanna L Kelley - Department of Genome Sciences, University of Washington, Seattle, WA, USA. jlkelley@uchicago.eduJan E AagaardMichael J MacCossWillie J Swanson
- Publication Details
- Journal of molecular evolution, Vol.71(2), pp.111-118
- Academic Unit
- Kelley Lab; Biological Sciences, School of
- Publisher
- Germany
- Grant note
- P41 RR011823 / NCRR NIH HHS HD042536 / NICHD NIH HHS GM72861 / NIGMS NIH HHS
- Identifiers
- 99900546564601842
- Language
- English
- Resource Type
- Journal article