Uemura M, Gilmour S J, Thomashow M F, Steponkus P L
Department of Soil, Crop and Atmospheric Sciences, Cornell University, Ithaca, New York 14853, USA.
Plant Physiol. 1996 May;111(1):313-27. doi: 10.1104/pp.111.1.313.
Several cold-regulated (COR) polypeptides, which have little or no amino acid sequence identity with known proteins, are synthesized during cold acclimation of Arabidopsis thaliana. However, the function of the polypeptides has yet to be elucidated. The objective of this study was to determine if COR6.6 and COR15am influence the incidence of either freeze-induced fusion or freeze-induced leakage of small unilamellar vesicles (SUVs) composed of either a single species of phosphatidylcholine (either 1-palmitoyl-2-oleoyl-,dioleoyl-, or dilinoleoylphosphatidylcholine), a mixture of dioleoylphosphatidylcholine, dioleoylphosphatidylethanolamine, and free sterols (1:1:1, mol:mol), or the total lipid extract of the plasma membrane of either nonacclimated or cold-acclimated rye leaves. When the SUVs were suspended in a dilute tris(hydroxymethyl)-aminomethane/2-(N-morpholino) ethanesulfonic acid buffer, both COR6.6 and COR15am invariably decreased the incidence of freeze-induced fusion regardless of the lipid composition. However, if the SUVs were suspended in a dilute solution of either sucrose or NaCl, the COR polypeptides had little or no effect on the incidence of freeze-induced fusion. Moreover, the COR polypeptides did not decrease the incidence of freeze-induced leakage--regardless of whether the SUVs were suspended in either the dilute buffer alone or with added sucrose or NaCl. In fact, with SUVs composed of a single species of phosphatidylcholine suspended in the dilute buffer, the COR polypeptides resulted in an anomalous increase in freeze-induced leakage. When considered collectively, these results suggest that neither COR6.6 nor COR15am has a direct cryoprotective effect on SUVs frozen in vitro.
在拟南芥的冷驯化过程中会合成几种冷调节（COR）多肽，这些多肽与已知蛋白质的氨基酸序列几乎没有或完全没有同一性。然而，这些多肽的功能尚未阐明。本研究的目的是确定COR6.6和COR15am是否会影响由单一磷脂酰胆碱（1-棕榈酰-2-油酰-、二油酰-或二亚油酰磷脂酰胆碱）、二油酰磷脂酰胆碱、二油酰磷脂酰乙醇胺和游离固醇的混合物（1:1:1，摩尔比）或未驯化或冷驯化黑麦叶片质膜的总脂质提取物组成的小单层囊泡（SUV）的冷冻诱导融合或冷冻诱导泄漏的发生率。当SUV悬浮在稀的三（羟甲基）氨基甲烷/2-（N-吗啉代）乙磺酸缓冲液中时，无论脂质组成如何，COR6.6和COR15am都始终会降低冷冻诱导融合的发生率。然而，如果将SUV悬浮在蔗糖或氯化钠的稀溶液中，COR多肽对冷冻诱导融合的发生率几乎没有影响。此外，COR多肽不会降低冷冻诱导泄漏的发生率——无论SUV是单独悬浮在稀缓冲液中还是添加了蔗糖或氯化钠。事实上，对于由单一磷脂酰胆碱组成并悬浮在稀缓冲液中的SUV，COR多肽会导致冷冻诱导泄漏异常增加。综合考虑这些结果表明，COR6.6和COR15am对体外冷冻的SUV均没有直接的冷冻保护作用。
