TY - JOUR
T1 - Functional characterization and metal ion specificity of the metal-citrate complex transporter from Streptomyces coelicolor
AU - Lensbouer, Joshua J.
AU - Patel, Ami
AU - Sirianni, Joseph P.
AU - Doyle, Robert P.
PY - 2008/8
Y1 - 2008/8
N2 - Secondary transporters of citrate in complex with metal ions belong to the bacterial CitMHS family, about which little is known. The transport of metal-citrate complexes in Streptomyces coelicolor has been investigated. The best cofactor for citrate uptake in Streptomyces coelicolor is Fe3+, but uptake was also noted for Ca2+, Pb2+, Ba2+, and Mn2+. Uptake was not observed with the Mg2+, Ni 2+, or Co2+ cofactor. The transportation of iron-and calcium-citrate makes these systems unique among the CitMHS family members reported to date. No complementary uptake akin to that observed for the CitH (Ca2+, Ba2+, Sr2+) and CitM (Mg2+, Ni2+, Mn2+, Co2+, Zn2+) systems of Bacillus subtilis was noted. Competitive experiments using EGTA confirmed that metal-citrate complex formation promoted citrate uptake. Uptake of free citrate was not observed. The open reading frame postulated as being responsible for the metal-citrate transport observed in Streptomyces coelicolor was cloned and overexpressed in Escherichia coli strains with the primary Fe 3+-citrate transport system (fecABCDE) removed. Functional expression was successful, with uptake of Ca2+-citrate, Fe3+- citrate, and Pb2+-citrate observed. No free-citrate transport was observed in IPTG (isopropyl-β-D-thiogalactopyranoside)-induced or -uninduced E. coli. Metabolism of the Fe3+-citrate and Ca 2+-citrate complexes, but not the Pb2+-citrate complex, was observed. Rationalization is based on the difference in metal-complex coordination upon binding of the metal by citrate.
AB - Secondary transporters of citrate in complex with metal ions belong to the bacterial CitMHS family, about which little is known. The transport of metal-citrate complexes in Streptomyces coelicolor has been investigated. The best cofactor for citrate uptake in Streptomyces coelicolor is Fe3+, but uptake was also noted for Ca2+, Pb2+, Ba2+, and Mn2+. Uptake was not observed with the Mg2+, Ni 2+, or Co2+ cofactor. The transportation of iron-and calcium-citrate makes these systems unique among the CitMHS family members reported to date. No complementary uptake akin to that observed for the CitH (Ca2+, Ba2+, Sr2+) and CitM (Mg2+, Ni2+, Mn2+, Co2+, Zn2+) systems of Bacillus subtilis was noted. Competitive experiments using EGTA confirmed that metal-citrate complex formation promoted citrate uptake. Uptake of free citrate was not observed. The open reading frame postulated as being responsible for the metal-citrate transport observed in Streptomyces coelicolor was cloned and overexpressed in Escherichia coli strains with the primary Fe 3+-citrate transport system (fecABCDE) removed. Functional expression was successful, with uptake of Ca2+-citrate, Fe3+- citrate, and Pb2+-citrate observed. No free-citrate transport was observed in IPTG (isopropyl-β-D-thiogalactopyranoside)-induced or -uninduced E. coli. Metabolism of the Fe3+-citrate and Ca 2+-citrate complexes, but not the Pb2+-citrate complex, was observed. Rationalization is based on the difference in metal-complex coordination upon binding of the metal by citrate.
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U2 - 10.1128/JB.00456-08
DO - 10.1128/JB.00456-08
M3 - Article
C2 - 18556792
AN - SCOPUS:49449108805
SN - 0021-9193
VL - 190
SP - 5616
EP - 5623
JO - Journal of bacteriology
JF - Journal of bacteriology
IS - 16
ER -