Chlamydomonas reinhardtii has multiple prolyl 4-hydroxylases, one of which is essential for proper cell wall assembly
Chlamydomonas reinhardtii has multiple prolyl 4-hydroxylases, one of which is essential for proper cell wall assembly
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DOI：
10.1105/tpc.106.042739
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发表时间：
2007-01-01
期刊：
影响因子：
11.6
通讯作者：
Myllyharju, Johanna
中科院分区：
文献类型：
--
作者：
Keskiaho, Katriina;Hieta, Reija;Myllyharju, Johanna
4-羟基脯氨酸酶(P4Hs)催化4-羟基脯氨酸(4Hyp)的形成，而4-羟基脯氨酸存在于许多植物糖蛋白中。我们克隆并鉴定了一种类似10P4H的莱茵衣藻多肽--Cr-P4H-1。重组Cr-P4H-1是一种29kD的可溶性单体，在体外能有效地羟化多聚(L-Pro)和衣藻细胞壁富含糖蛋白(HRGP)GP1中富含Pro基序的合成肽。类似的富含Pro的重复序列很可能是铬-P4H-1底物，也存在于细胞壁、HRGP、GP2和可能的GP3中。通过RNA干扰抑制编码Cr-P4H-1的基因导致细胞壁缺陷，细胞壁由疏松的纤维网络组成，类似于野生型壁的内外W1和W7层，而形成致密的中心三联体的层缺失。缺乏Cr-P4H-1很可能影响中央三联体的主要HRPG的4Hyp含量，即GP1、GP2和GP3。这些HRGP中降低的4Hyp水平预计也会影响它们的糖基化，从而影响它们的纤维轴的相互作用特性和稳定性。有趣的是，我们的RNA干扰数据表明，其他9个衣藻P4H样多肽不能完全弥补Cr-P4H-1活性的缺乏，因此可能具有不同的底物特异性和功能。
Prolyl 4-hydroxylases (P4Hs) catalyze formation of 4-hydroxyproline (4Hyp), which is found in many plant glycoproteins. We cloned and characterized Cr-P4H-1, one of 10P4H-like Chlamydomonas reinhardtii polypeptides. Recombinant Cr-P4H-1 is a soluble 29-kD monomer that effectively hydroxylated in vitro both poly( L-Pro) and synthetic peptides representing Pro-rich motifs found in the Chlamydomonas cell wall Hyp-rich glycoprotein ( HRGP) GP1. Similar Pro-rich repeats that are likely to be Cr-P4H-1 substrates are also present in the cell wall HRGP GP2 and probably GP3. Suppression of the gene encoding Cr-P4H-1 by RNA interference led to a defective cell wall consisting of a loose network of fibrils resembling the inner and outer W1 and W7 layers of the wild-type wall, while the layers forming the dense central triplet were absent. The lack of Cr-P4H-1 most probably affected 4Hyp content of the major HRPGs of the central triplet, GP1, GP2, and GP3. The reduced 4Hyp levels in these HRGPs can also be expected to affect their glycosylation and, thus, the interactive properties and stabilities of their fibrous shafts. Interestingly, our RNA interference data indicate that the nine other Chlamydomonas P4H-like polypeptides could not fully compensate for the lack of Cr-P4H-1 activity and are therefore likely to have different substrate specificities and functions.