Cell wall core galactofuran synthesis is essential for growth of mycobacteria
Cell wall core galactofuran synthesis is essential for growth of mycobacteria
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DOI：
10.1128/jb.183.13.3991-3998.2001
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发表时间：
2001-07-01
影响因子：
3.2
通讯作者：
McNeil, M
中科院分区：
文献类型：
--
作者：
Pan, F;Jackson, M;McNeil, M
分枝杆菌细胞壁核心由外部脂质（分枝菌酸）层组成，该外部脂质层通过含有呋喃半乳糖基的多糖阿拉伯半乳聚糖附着在肽聚糖上。这种结构排列强烈表明呋喃半乳糖基残基对于分枝杆菌的生长和生存至关重要，呋喃半乳糖基残基在自然界中是通过 UDP-吡喃半乳糖变位酶 (Glf) 催化的 UDP-吡喃半乳糖环收缩为 UDP-呋喃半乳糖而形成的。在结核分枝杆菌中，glf 基因与 Rv3808c 基因有 1 个核苷酸重叠，该基因已被证明编码呋喃半乳糖基转移酶。我们在这里证明，只有在两个携带glf和Rv3808c功能性拷贝的拯救质粒存在的情况下，glf才能在耻垢分枝杆菌中通过等位基因替换被敲除。 glf救援质粒被设计为具有温度敏感的复制起点，并且耻垢分枝杆菌glf敲除突变体不能在含有glf的救援质粒丢失的较高温度下生长。在单独的实验中，Rv3808c救援质粒被设计为具有温度敏感的复制起点，而带有glf的质粒被设计为具有正常的复制起点；该菌株在不允许的温度下也无法生长。因此，glf 和 Rv3808c 对于生长都是必需的。这些发现以及在人体中未发现呋喃半乳糖基残基的事实支持开发UDP-吡喃半乳糖变位酶和呋喃半乳糖基转移酶作为开发新抗结核药物的重要靶标。
The mycobacterial cell wall core consists of an outer lipid (mycolic acid) layer attached to peptidoglycan via a galactofuranosyl-containing polysaccharide, arabinogalactan. This structural arrangement strongly suggests that galactofuranosyl residues are essential for the growth and viability of mycobacteria, Galactofuranosyl residues are formed in nature by a ring contraction of UDP-galactopyranose to UDP-galactofuranose catalyzed by the enzyme UDP-galactopyranose mutase (Glf). In Mycobacterium tuberculosis the glf gene overlaps, by 1 nucleotide, a gene, Rv3808c, that has been shown to encode a galactofuranosyl transferase. We demonstrate here that glf can be knocked out in Mycobacterium smegmatis by allelic replacement only in the presence of two rescue plasmids carrying functional copies of glf and Rv3808c. The glf rescue plasmid was designed with a temperature-sensitive origin of replication and the M, smegmatis glf knockout mutant is unable to grow at the higher temperature at which the glf-containing rescue plasmid is lost. In a separate experiment, the Rv3808c rescue plasmid was designed with a temperature-sensitive origin of replication and the glf-bearing plasmid was designed with a normal original of replication; this strain was also unable to grow at the nonpermissive temperature. Thus, both glf and Rv3808c are essential for growth. These findings and the fact that galactofuranosyl residues are not found in humans supports the development of UDP-galactopyranose mutase and galactofuranosyl transferase as important targets for the development of new antituberculosis drugs.