A nested gene in Streptomyces bacteria encodes a protein involved in quaternary complex formation

作者：Kallio Pauli; Liu Zhanliang; Mantsala Pekka; Niemi Jarmo; Metsa Ketela Mikko^*

来源：Journal of Molecular Biology, 2008, 375(5): 1212-1221.

DOI：10.1016/j.jmb.2007.11.044

• overlapping gene
• nested gene
• polyketide biosynthesis
• protein synthesis
• Streptomyces

The gene pgaM is involved in the biosynthesis of an angucycline-type polyketide antibiotic in Streptomyces sp. PGA64. It encodes a two-domain polypeptide consisting of an N-terminal flavoprotein oxygenase and a C-terminal short-chain alcohol. dehydrogenase/reductase, which are fused together at the translational level as a result of end codon deletion. Here we show that translation also initiates at an internal start codon that enables independent expression of a separate reductase subunit, PgaMred. This confirms that the gene exhibits a rare viral-like arrangement of two overlapping reading frames that allows simultaneous expression of two alternative forms of the protein. Together, these two proteins associate to form a stable non-covalent complex, the native form of PgaM. The reductase subunit PgaMred is shown to provide enzyme stability and to affect the redox state of the oxygenase domain FAD. Finally, a model for the quaternary structure of the complex that explains the necessity for a nested gene system and the unusual behaviour of the protein subunits in vitro is presented.

• 出版日期2008-2-1
• 单位河北农业大学