NEW MAP LOCATION OF ilvO IN ESCHERICHIA COLI

[摘要] Mutations in ilvO , the operator site for operon A of the ilv region of E. coli K-12, are reported to cause a cis dominant derepression of the operon A gene products and to map between ilvC and ilvA . Studies reported here demonstrate that the F25 episome which does not carry the region between ilvC and ilvA but only ilvE, ilvD and a part of ilvA , can transfer ilvO genetic material. Also, genes of operon A on the F25 episome respond normally to a derepression signal. It is proposed that ilvO is on the F25 episome. Five-point crosses demonstrate that mutations in ilvO map nearer to ilvE than to ilvA . Considering this and other evidence, it is proposed that the gene order in the ilv region is CADEO, not COADE, with transcription and translation in operon A being from ilvE to ilvA not ilvA to ilvE . It is confirmed that mutations in ilvO cause a cis dominant derepression of the operon A gene products but it is also noted that mutations in ilvO lead to the appearance of an AHAS activity more resistant to inhibition by valine than that of the present O+ strain.

[学科分类] 医学（综合）