• Microbiology and Biotechnology Letters
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• v.31 no.3
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• pp.307-310
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• 2003

A gene encoding streptodornase(sdc) from Streptococcus equisimilis H46A was expressed in S. equisimilis H64H sdc under the control of the streptokinase gene promoter. Secretion of the streptodornase was directed by the signal sequences of streptokinase or streptodornase. The expressed streptodornase activity from S. equisimilis H46A sdc transformant with streptokinase promoter - streptodornase coding sequence fusion vector was 2.3 fold higher than that from wild type. Construct of signal sequence region replaced by streptokinase ones was similarly expressed as a wild type. But constructs of skc or lrp core regions of streptokinase promoter streptodornase fusion were similarly expressed as in sdc mutant. In conclusion, improved expression of streptodornase by use of streptokinase promoter required the full length of promoter.

• Journal of Microbiology and Biotechnology
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• v.20 no.1
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• pp.132-137
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• 2010

The skc gene encoding streptokinase (SK) with a molecular mass of approximately 47.4 kDa was cloned from Streptococcus equisimilis ATCC 9542 and heterologously overexpressed in Streptomyces lividans TK24 and E. coli using various strong promoters. When the promoter for sprT [Streptomyces griseus trypsin (SGT)] was used in the host S. lividans TK24, a 47.4-kDa protein was detected along with a smaller hydrolyzed protein (44 kDa), suggesting that posttranslational hydrolysis had occurred as has been reported in other expression systems. The casein/plasminogen plate assay revealed that the plasmid construct containing the SGT signal peptide was superior to that containing the SK signal peptide in terms of SK production. Maximal production of SK was calculated to be about 0.25 unit/ml of culture broth, a value that was five times higher than that obtained with other expression systems using ermE and tipA promoters in the same host. When the skc gene was expressed in E. coli BL21(${\Delta}DE3$)pLys under the control of the T7 promoter, a relatively large amount of SK was expressed in soluble form without hydrolysis. SK activity in E. coli/pET28a-$T7_pSK_m$ was more than 2 units/ml of culture broth, even though about half of the expressed protein formed an inactive inclusion body.