• Korean Journal of Microbiology
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• v.51 no.3
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• pp.256-262
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• 2015

In order to study the effect of the receptor protein (SeaR), which is isolated from Saccharopolyspora erythraea, we introduced the SeaR gene to Streptomyces virginiae as host strains. An effective transformation procedure for S. virginiae was established based on transconjugation by Escherichia coli ET12567/pUZ8002 with a ${\varphi}C31$-derived integration vector, pSET152, which contained int, oriT, attP, and $ermEp^{\ast}$ (erythromycin promotor). Therefore, the pEV615 was introduced into S. virginiae by conjugation and integrated at the attB locus in the chromosome of the recipients by the ${\varphi}C31$ integrase (int) function. Transformants of S. virginiae containing the SeaR gene were confirmed by PCR and transcriptional expression of the SeaR gene in the transformants was analyzed by RT-PCR, respectively. And, we examined the production time of virginiamycins in the culture media of both the transformants and the wild type. The production time of virginiamycins in the wild type and transformants was the same. When 100 ng/ml of synthetic $VB-C_6$ was added to the state of 6 or 8 hour cultivation of wild type and transformants, respectively, the virginiamycins production was induced, meaning that the virginiamycins production in the wild type was detected 2 h early than transformants. From these results, SeaR expression was also affected to virginiamycins production in transformants derived from S. virginiae. In this study, we showed that the SeaR protein worked as a repressor in transformants.

• The Korean Journal of Financial Management
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• v.24 no.2
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• pp.1-40
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• 2007

We test a model of investment-cashflow-growth opportunities relationship in order to estimate the sensitivities to investments. In this study, we use a new proxy variable for the value of growth opportunities(hereafter "VGO"), which is based on the seminal papers of M&M(1958:1961:1963) and Lee(2006;2007). The empirical findings on the sensitivities of cashflow and growth opportunities are as follows. First, when the traditional proxy variables for the growth opportunities such as Tobin's Q, MBR and sales growth are included with the new proxy VGO in the estimation, their coefficients are turned out to be insignificant. Second, only the new proxy variable VGO shows a statistically significant positive sensitibity to investment, which can be regarded that the growth opportunities hold the positive influences to investments. Third, the Tobin's Q can be decomposed into three factors such as the value of growth opportunities(VGO), the value of asset-in-place and valuation errors. It turns out that only the VGO shows a statistically significant positive relationship with investment among others. This means that the new variable VGO is a good proxy variable for the growth opportunities in the investment-cashflow sensitivity analysis. In sum, thanks to the above findings in this study, we can say that it will not be proper to choose a proxy variable for the growth opportunities from the traditional set of proxies such as Tobin's Q, MBR, or sales growth rate.