L-glutamate enhances the expression of Thermus maltogenic amylase in Escherichia coli.
Escherichia coli BL21 (DE3) transformed with a thermostable Thermus maltogenic amylase (ThMA), isolated from a Gram-negative bacterium Thermus strain IM6501, grew well and efficiently produced ThMA in a complex medium but not in a chemically defined medium (DM). By supplementing L-glutamate to DM medium, both the specific growth rate and ThMA expression significantly increased. Alterations in the cellular responses of recombinant E. coli to L-glutamate were analyzed at the protein level by two-dimensional gel electrophoresis and mass spectrometry. The ppGpp synthase (RelA) was significantly reduced in cells grown with L-glutamate and was consistent with the low level of ppGpp, an indicator of stringent response. On the other hand, protein chain elongation factor (EF-Tu) and manganese-containing superoxide dismutase (MnSOD), which protects cells against oxidative damage, was significantly elevated by L-glutamate supplementation. These results indicate that L-glutamate enhances ThMA expression and increases the E. coli growth rate not only by overcoming the stringent response but also by increasing the synthesis of EF-Tu and MnSOD.
Jung
Hyung-Moo
HM
BioNgene Co., Ltd., 10-1, 1Ka, Myungryun-Dong, Jongro-Ku, Seoul 110-521, Korea.
Park
Kwan-Hwa
KH
Kim
Sang-Yong
SY
Lee
Jung-Kul
JK
D001426:Bacterial Proteins / Q000378:metabolism; D002455:Cell Division / Q000187:drug effects; D002470:Cell Survival / Q000187:drug effects; D004305:Dose-Response Relationship, Drug; D004926:Escherichia coli / Q000166:cytology / Q000187:drug effects / Q000254:growth & development* / Q000378:metabolism*; D015964:Gene Expression Regulation, Bacterial / Q000187:drug effects; D018698:Glutamic Acid / Q000494:pharmacology*; D006026:Glycoside Hydrolases / Q000096:biosynthesis* / Q000235:genetics; D015202:Protein Engineering / Q000379:methods*; D011994:Recombinant Proteins / Q000096:biosynthesis; D013824:Thermus / Q000201:enzymology* / Q000235:genetics
D001426:Bacterial Proteins; D011994:Recombinant Proteins; D018698:Glutamic Acid; D006026:Glycoside Hydrolases; C120909:glucan 1,4-alpha-maltohydrolase