PDF(Pubmed)
Abstract：
Peptidoglycan is an essential component of the bacterial cell envelope that contains glycan chains substituted by short peptide stems. Peptide stems are polymerized by D,D-transpeptidases, which make bonds between the amino acid in position four of a donor stem and the third residue of an acceptor stem (4-3 cross-links). Some bacterial peptidoglycans also contain 3-3 cross-links that are formed by another class of enzymes called L,D-transpeptidases which contain a YkuD catalytic domain. In this work, we investigate the formation of unusual bacterial 1-3 peptidoglycan cross-links. We describe a version of the PGFinder software that can identify 1-3 cross-links and report the high-resolution peptidoglycan structure of Gluconobacter oxydans (a model organism within the Acetobacteraceae family). We reveal that G. oxydans peptidoglycan contains peptide stems made of a single alanine as well as several dipeptide stems with unusual amino acids at their C-terminus. Using a bioinformatics approach, we identified a G. oxydans mutant from a transposon library with a drastic reduction in 1-3 cross-links. Through complementation experiments in G. oxydans and recombinant protein production in a heterologous host, we identify an L,D-transpeptidase enzyme with a domain distantly related to the YkuD domain responsible for these non-canonical reactions. This work revisits the enzymatic capabilities of L,D-transpeptidases, a versatile family of enzymes that play a key role in bacterial peptidoglycan remodelling.
摘要：
肽聚糖是细菌细胞包膜的基本组分,其含有被短肽茎取代的聚糖链。肽茎由D聚合，D-转肽酶,在供体茎4位的氨基酸和受体茎的第三个残基之间形成键（4-3个交联）。一些细菌肽聚糖还含有3-3个交联，这些交联是由另一类称为L，含有YkuD催化结构域的D-转肽酶。在这项工作中,我们研究了不寻常的细菌1-3肽聚糖交联的形成。我们描述了PGFinder软件的一个版本，该软件可以识别1-3个交联，并报告了氧化葡糖杆菌（乙酰杆菌科的模型生物）的高分辨率肽聚糖结构。我们揭示了氧化酵母肽聚糖含有由单个丙氨酸组成的肽茎以及在其C末端具有不寻常氨基酸的几个二肽茎。使用生物信息学方法，我们从转座子文库中鉴定出2个氧化黑曲霉突变体，其中1-3个交联显著减少。通过在异源宿主中的氧化黑曲霉和重组蛋白生产的互补实验，我们识别一个L,D-转肽酶，其结构域与负责这些非规范反应的YkuD结构域远近相关。这项工作重新审视了L，D-转肽酶,一个在细菌肽聚糖重塑中起关键作用的多功能酶家族。
