SanT, a bidomain protein, is essential for nikkomycin biosynthesis of Streptomyces ansochromogenes.
Nikkomycins act as a competitive inhibitor of chitin synthetase and display potent activities against phytopathogenic and human pathogenic fungi. sanT is located in the gene cluster of nikkomycin biosynthesis in Streptomyces ansochromogenes. Sequence analysis revealed that the deduced product of sanT has an unusual domain structure, which consists of an N-terminal acyl carrier protein (ACP) domain and a C-terminal aminotransferase (AMT) domain. Gene disruption and complementation indicated that sanT is essential for nikkomycin biosynthesis. Each domain of SanT was overexpressed in Escherichia coli and then purified. ACP domain is posttranslationally modified with phosphopantetheine (Ppant) prosthetic group at Ser-33. AMT domain catalyzes the transamination of 4-pyridyl-2-oxo-4-hydroxyisovalerate (POHIV), a precursor of peptidyl moiety of nikkomycins, to pyridylhomothreonine (PHT) in vitro. The two domains function independently but both are essential for nikkomycin biosynthesis. The biochemical and genetic evidences suggested that SanT is possibly a bifunctional protein, participating in the biosynthesis of peptidyl moiety and the assembly of nikkomycins.
Jia
Lianghui
L
State Key Laboratory of Microbial Resources, Institute of Microbiology, Graduate School of Chinese Academy of Sciences, Beijing 100039, China.
Tian
Yuqing
Y
Tan
Huarong
H
D000595:Amino Acid Sequence; D000617:Aminoglycosides / Q000096:biosynthesis*; D008969:Molecular Sequence Data; D017434:Protein Structure, Tertiary; D015398:Signal Transduction / Q000502:physiology*; D013302:Streptomyces / Q000145:classification / Q000378:metabolism*; D035381:TATA-Binding Protein Associated Factors / Q000737:chemistry* / Q000378:metabolism*