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KMID : 0545120040140030520
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Journal of Microbiology and Biotechnology
2004 Volume.14 No. 3 p.520 ~ p.524
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Cloning of a Novel Na(+)-Dependent L-Serine Specific Symporter Gene from Haemophilus influenzae Rd and Characteristics of the Transporter
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Kim YM
Rhee IK/Tsuchiya T
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Abstract
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A protein that exhibited a high similarity to a major serine transporter of Escherichia coli SdaC was found in Haemophilus influenzae Rd. Also Na+-stimulated serine transport activity was detected in the cells. The sdaC of H. influenzae was cloned and the properties of the transporter were investigated. The activity of serine transport was stimulated by Na+. Uptake of Na+ elicited by L-serine influx into cells was also observed which supports the idea that Lserine is transported by a mechanism of Na+/serine symport. No uptake of H+ elicited by L-serine influx was detected. This result was not consistent with that obtained with the homologous protein SdaC of E. coli which uses H+ as a coupling cation. The serine transport via the SdaC of H. influenzae was not inhibited by other amino acids such as threonine or D-serine like the SdaC of E. coli. Thus the SdaC of H. influenzae is a Na+-dependent L-serine specific symporter and an unusual natural mutant. The Km and the Vmax value for the serine transport in the SdaC of H. influenzae were 7.6 mM and 22.9 nmol/min/mg protein respectively.
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KEYWORD
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