Conserved sequence motifs in human TMTC1, TMTC2, TMTC3, and TMTC4, new O-mannosyltransferases from the GT-C/PMT clan, are rationalized as ligand binding sites.
Conserved sequence motifs in human TMTC1, TMTC2, TMTC3, and TMTC4, new O-mannosyltransferases from the GT-C/PMT clan, are rationalized as ligand binding sites.
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DOI：
10.1186/s13062-021-00291-w
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发表时间：
2021-01-12
期刊：
影响因子：
5.5
通讯作者：
Eisenhaber F
中科院分区：
文献类型：
--
作者：
Eisenhaber B;Sinha S;Jadalanki CK;Shitov VA;Tan QW;Sirota FL;Eisenhaber F
人类蛋白TMTC1、TMTC2、TMTC3和TMTC4已被实验证明是一种新的o -甘露糖基化途径的组成部分。它们本身的甘露糖基转移酶活性已被怀疑，但其实际的酶促潜能尚未得到证实。到目前为止，TMTCs的序列分析一直受到其膜内嵌入n端区域的进化序列分歧，蛋白质数据库中的序列不准确以及难以解释已知同源蛋白（主要是糖转移酶和一些已知的3D结构）的大量功能变化的影响。TMTCs之间的进化保守分子功能只有在其膜嵌入的n端区域内具有保守的膜拓扑才能实现，从而导致同源的长间歇环在同一膜侧的放置。利用这一标准，我们证明了所有TMTCs都有11个跨膜区域。与Pfam模型DUF1736同源的序列片段实际上只是TM7和TM8之间的一个环，位于内质网腔内，包含一个小的疏水螺旋，但不是膜嵌入螺旋。TMTCs的膜嵌入n端区域不仅与GT-C糖转移酶亚群具有共同的折叠和3D结构相似性。对催化、二价金属离子结合和脂质糖部分磷酸基的关键残基在酶学和结构上进行了充分研究的GT-Cs和TMTCs序列中都得到了保存，这表明TMTCs实际上是糖转移酶。我们提出了所有四种TMTCs的可靠的三维结构模型（来源于它们最接近的已知同源物5ezm/5f15），并发现观察到的保守序列基序被合理化为金属离子和多羟基-磷酸-甘露糖部分的结合位点。根据仔细的序列分析和结构建模的结果，我们可以得出结论，tmtc是酶活性糖转移酶，属于GT-C/PMT超家族。DUF1736片段是TM7和TM8之间的环，对催化和脂联糖片段结合至关重要。结合现有的间接实验数据，我们得出结论，tmtc不仅是上真核生物内质网中o -甘露糖基化途径的一部分，而且实际上是人们所寻求的甘露糖基转移酶。在线版本包含补充材料，可在10.1186/s13062-021-00291-w获得。
The human proteins TMTC1, TMTC2, TMTC3 and TMTC4 have been experimentally shown to be components of a new O-mannosylation pathway. Their own mannosyl-transferase activity has been suspected but their actual enzymatic potential has not been demonstrated yet. So far, sequence analysis of TMTCs has been compromised by evolutionary sequence divergence within their membrane-embedded N-terminal region, sequence inaccuracies in the protein databases and the difficulty to interpret the large functional variety of known homologous proteins (mostly sugar transferases and some with known 3D structure). Evolutionary conserved molecular function among TMTCs is only possible with conserved membrane topology within their membrane-embedded N-terminal regions leading to the placement of homologous long intermittent loops at the same membrane side. Using this criterion, we demonstrate that all TMTCs have 11 transmembrane regions. The sequence segment homologous to Pfam model DUF1736 is actually just a loop between TM7 and TM8 that is located in the ER lumen and that contains a small hydrophobic, but not membrane-embedded helix. Not only do the membrane-embedded N-terminal regions of TMTCs share a common fold and 3D structural similarity with subgroups of GT-C sugar transferases. The conservation of residues critical for catalysis, for binding of a divalent metal ion and of the phosphate group of a lipid-linked sugar moiety throughout enzymatically and structurally well-studied GT-Cs and sequences of TMTCs indicates that TMTCs are actually sugar-transferring enzymes. We present credible 3D structural models of all four TMTCs (derived from their closest known homologues 5ezm/5f15) and find observed conserved sequence motifs rationalized as binding sites for a metal ion and for a dolichyl-phosphate-mannose moiety. With the results from both careful sequence analysis and structural modelling, we can conclusively say that the TMTCs are enzymatically active sugar transferases belonging to the GT-C/PMT superfamily. The DUF1736 segment, the loop between TM7 and TM8, is critical for catalysis and lipid-linked sugar moiety binding. Together with the available indirect experimental data, we conclude that the TMTCs are not only part of an O-mannosylation pathway in the endoplasmic reticulum of upper eukaryotes but, actually, they are the sought mannosyl-transferases. The online version contains supplementary material available at 10.1186/s13062-021-00291-w.
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影响因子：
16.6
作者：
Choquet H;Paylakhi S;Kneeland SC;Thai KK;Hoffmann TJ;Yin J;Kvale MN;Banda Y;Tolman NG;Williams PA;Schaefer C;Melles RB;Risch N;John SWM;Nair KS;Jorgenson E
通讯作者：
Jorgenson E
影响因子：
2
作者：
Guillen-Ahlers H;Erbe CB;Chevalier FD;Montoya MJ;Zimmerman KD;Langefeld CD;Olivier M;Runge CL
通讯作者：
Runge CL
影响因子：
3.7
作者：
Cao D;Jiao X;Liu X;Hennis A;Leske MC;Nemesure B;Hejtmancik JF
通讯作者：
Hejtmancik JF
DOI：
10.1093/protein/15.9.745
发表时间：
2002-09-01
期刊：
PROTEIN ENGINEERING
影响因子：
--
作者：
Cserzö, M;Eisenhaber, F;Simon, I
通讯作者：
Simon, I
影响因子：
5.4
作者：
Baker JA;Wong WC;Eisenhaber B;Warwicker J;Eisenhaber F
通讯作者：
Eisenhaber F