Raymond James A, Janech Michael G, Fritsen Christian H
School of Life Sciences, University of Nevada, Las Vegas, Nevada 89154, USAMedical University of South Carolina, Charleston, South Carolina 29425, USADesert Research Institute, Reno, Nevada 89557, USA.
J Phycol. 2009 Feb;45(1):130-6. doi: 10.1111/j.1529-8817.2008.00623.x. Epub 2009 Feb 3.
Many cold-adapted unicellular plants express ice-active proteins, but at present, only one type of such proteins has been described, and it shows no resemblance to higher plant antifreezes. Here, we describe four isoforms of a second and very active type of extracellular ice-binding protein (IBP) from a unicellular chlamydomonad alga collected from an Antarctic intertidal location. The alga is a euryhaline psychrophile that, based on sequences of the alpha tubulin gene and an IBP gene, appears to be the same as a snow alga collected on Petrel Island, Antarctica. The IBPs, which do not resemble any known antifreezes, have strong recrystallization inhibition activity and have an ability to slow the drainage of brine from sea ice. These properties, by maintaining liquid environments, may increase survival of the cells in freezing environments. The IBPs have a repeating TXT motif, which has previously been implicated in ice binding in insect antifreezes and a ryegrass antifreeze.
许多适应寒冷的单细胞植物会表达冰活性蛋白，但目前，此类蛋白仅被描述过一种，且它与高等植物的抗冻蛋白并无相似之处。在此，我们描述了从南极潮间带采集的一种单细胞衣藻中第二种极具活性的细胞外冰结合蛋白（IBP）的四种同工型。该藻类是一种广盐性嗜冷生物，基于α微管蛋白基因和一种IBP基因的序列，它似乎与在南极海燕岛采集的一种雪藻相同。这些IBP与任何已知的抗冻蛋白均不相似，具有很强的重结晶抑制活性，并有能力减缓海冰中盐水的排出。通过维持液体环境，这些特性可能会提高细胞在冰冻环境中的存活率。这些IBP具有重复的TXT基序，此前已发现该基序与昆虫抗冻蛋白和黑麦草抗冻蛋白中的冰结合有关。
