Phytosulfokine-alpha, a sulfated pentapeptide, stimulates the proliferation of rice cells by means of specific high-and low-affinity binding sites
Phytosulfokine-alpha, a sulfated pentapeptide, stimulates the proliferation of rice cells by means of specific high-and low-affinity binding sites
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DOI：
10.1073/pnas.94.24.13357
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发表时间：
1997-11-25
影响因子：
11.1
通讯作者：
Sakagami, Y
中科院分区：
文献类型：
--
作者：
Matsubayashi, Y;Takagi, L;Sakagami, Y
从水稻 (Oryza sativa L.) 悬浮培养物的条件培养基中分离出肽生长因子，并鉴定为硫酸化五肽 [H-Tyr(SO3H)-Ile-Tyr(SO3H)-Thr-Gln-OH] 及其 C 端截短的四肽 [H-Tyr(SO3H)-Ile-Tyr(SO3H)-Thr-OH]。这些结构与最初在芦笋（Asparagus officinalis L.）叶肉培养物中发现的植物硫因子相同。五肽[植物硫因子-α (PSK-α)]在浓度高于10(-8) M时非常强烈地刺激水稻原生质体的集落形成，表明植物硫因子在水稻中具有类似的作用模式。使用 S-35 标记的 PSK-α 进行的结合测定表明，悬浮的水稻细胞表面存在高亲和力和低亲和力的特异性可饱和结合位点。对差速离心级分中[S-35]PSK-α结合的分析表明该结合与质膜富集级分相关。 [S-35]PSK-α 结合的表观 K-d 值，高亲和力类型为 1 x 10(-9) M，低亲和力类型为 1 x 10(-7) M，最大结合位点数量分别为每个细胞 1 x 10(4) 个位点和每个细胞 1 x 10(5) 个位点。 [S-35]PSK-α 和几种合成的 PSK-α 类似物的竞争研究表明，只有具有促有丝分裂活性的肽才能有效地取代放射性配体。这些结果表明肽因子介导的信号转导途径参与植物细胞增殖。
Peptide growth factors were isolated from conditioned medium derived from rice (Oryza sativa L.) suspension cultures and identified to be a sulfated pentapeptide [H-Tyr(SO3H)-Ile-Tyr(SO3H)-Thr-Gln-OH] and its C-terminal-truncated tetrapeptide [H-Tyr(SO3H)-Ile-Tyr(SO3H)-Thr-OH]. These structures were identical to the phytosulfokines originally found in asparagus (Asparagus officinalis L.) mesophyll cultures. The pentapeptide [phytosulfokine-alpha (PSK-alpha)] very strongly stimulated colony formation of rice protoplasts at concentrations above 10(-8) M, indicating a similar mode of action in rice of phytosulfokines. Binding assays using S-35-labeled PSK-alpha demonstrated the existence of both high-and low-affinity specific saturable binding sites on the surface of rice cells in suspension. Analysis of [S-35]PSK-alpha binding in differential centrifugation fractions suggested association of the binding with a plasma membrane-enriched fraction. The apparent K-d values for [S-35]PSK-alpha, binding were found to be 1 x 10(-9) M for the high-affinity type and 1 x 10(-7) M for the low-affinity type, with maximal numbers of binding sites of 1 x 10(4) sites per cell and 1 x 10(5) sites per cell, respectively. Competition studies with [S-35]PSK-alpha and several synthetic PSK-alpha analogs demonstrated that only peptides that possesses mitogenic activity can effectively displace the radioligand. These results suggest that a signal transduction pathway mediated by peptide factors is involved in plant cell proliferation.