Kobayashi M, Nakagawa H, Asaka T, Matoh T
Laboratory of Plant Nutrition, Division of Applied Life Sciences, Graduate School of Agriculture, Kyoto University, Kyoto 606-8502, Japan.
Plant Physiol. 1999 Jan;119(1):199-204. doi: 10.1104/pp.119.1.199.
The extent of in vitro formation of the borate-dimeric-rhamnogalacturonan II (RG-II) complex was stimulated by Ca2+. The complex formed in the presence of Ca2+ was more stable than that without Ca2+. A naturally occurring boron (B)-RG-II complex isolated from radish (Raphanus sativus L. cv Aokubi-daikon) root contained equimolar amounts of Ca2+ and B. Removal of the Ca2+ by trans-1,2-diaminocyclohexane-N,N,N',N'-tetraacetic acid induced cleavage of the complex into monomeric RG-II. These data suggest that Ca2+ is a normal component of the B-RG-II complex. Washing the crude cell walls of radish roots with a 1.5% (w/v) sodium dodecyl sulfate solution, pH 6.5, released 98% of the tissue Ca2+ but only 13% of the B and 22% of the pectic polysaccharides. The remaining Ca2+ was associated with RG-II. Extraction of the sodium dodecyl sulfate-washed cell walls with 50 mM trans-1,2-diaminocyclohexane-N, N,N',N'-tetraacetic acid, pH 6.5, removed the remaining Ca2+, 78% of B, and 49% of pectic polysaccharides. These results suggest that not only Ca2+ but also borate and Ca2+ cross-linking in the RG-II region retain so-called chelator-soluble pectic polysaccharides in cell walls.
硼酸二聚鼠李半乳糖醛酸聚糖II（RG-II）复合物的体外形成程度受到Ca2+的刺激。在Ca2+存在下形成的复合物比没有Ca2+时更稳定。从萝卜（Raphanus sativus L. cv Aokubi-daikon）根中分离出的天然硼（B）-RG-II复合物含有等摩尔量的Ca2+和B。用反式-1,2-二氨基环己烷-N,N,N',N'-四乙酸去除Ca2+会导致复合物裂解为单体RG-II。这些数据表明Ca2+是B-RG-II复合物的正常组成部分。用pH 6.5的1.5%（w/v）十二烷基硫酸钠溶液洗涤萝卜根的粗细胞壁，释放出98%的组织Ca2+，但仅释放出13%的B和22%的果胶多糖。剩余的Ca2+与RG-II相关。用pH 6.5的50 mM反式-1,2-二氨基环己烷-N,N,N',N'-四乙酸提取十二烷基硫酸钠洗涤过的细胞壁，去除了剩余的Ca2+、78%的B和49%的果胶多糖。这些结果表明，不仅Ca2+，而且RG-II区域中的硼酸盐和Ca2+交联都能将所谓的螯合剂可溶性果胶多糖保留在细胞壁中。
