Abstract
| Originalsprog | Engelsk |
|---|---|
| Tidsskrift | Journal of Bacteriology |
| Vol/bind | 184 |
| Udgave nummer | 12 |
| Sider (fra-til) | 3368-3376 |
| Antal sider | 8 |
| ISSN | 0021-9193 |
| DOI | |
| Status | Udgivet - 2002 |
Bibliografisk note
Keywords: Bacterial Proteins; Bacteriochlorophylls; Carbon-Oxygen Ligases; Chlorobi; Light-Harvesting Protein Complexes; Microscopy, Electron; Mutation; Organelles; Photosynthetic Reaction Center Complex Proteins; Pigments, BiologicalAdgang til dokumentet
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I: Journal of Bacteriology, Bind 184, Nr. 12, 2002, s. 3368-3376.
Publikation: Bidrag til tidsskrift › Tidsskriftartikel › Forskning › peer review
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TY - JOUR
T1 - Chlorobium tepidum mutant lacking bacteriochlorophyll c made by inactivation of the bchK gene, encoding bacteriochlorophyll c synthase
AU - Frigaard, Niels-Ulrik
AU - Voigt, Ginny D
AU - Bryant, Donald A
N1 - Keywords: Bacterial Proteins; Bacteriochlorophylls; Carbon-Oxygen Ligases; Chlorobi; Light-Harvesting Protein Complexes; Microscopy, Electron; Mutation; Organelles; Photosynthetic Reaction Center Complex Proteins; Pigments, Biological
PY - 2002
Y1 - 2002
N2 - The gene encoding bacteriochlorophyll (BChl) c synthase was identified by insertional inactivation in the photosynthetic green sulfur bacterium Chlorobium tepidum and was named bchK. The bchK mutant of C. tepidum was rusty-orange in color and completely lacked BChl c. Because of the absence of the BChl c antenna, the mutant grew about seven times slower than the wild type at light intensities that were limiting to the wild type (< 90 micromol m(-2) s(-1)). Various pheophorbides, which probably represent precursors of BChl c which had lost magnesium, accumulated in the mutant cells. A small fraction of these pheophorbides were apparently esterified by the remaining chlorophyll (Chl) a and BChl a synthases in cells. The amounts of BChl a, Chl a, isoprenoid quinones, carotenoids, Fenna-Matthews-Olson protein, and chlorosome envelope protein CsmA were not significantly altered on a cellular basis in the mutant compared to in the wild type. This suggests that the BChl a antennae, photosynthetic reaction centers, and remaining chlorosome components were essentially unaffected in the mutant. Electron microscopy of thin sections revealed that the mutant lacked normal chlorosomes. However, a fraction containing vestigial chlorosomes, denoted "carotenosomes," was partly purified by density centrifugation; these structures contained carotenoids, isoprenoid quinones, and a 798-nm-absorbing BChl a species that is probably protein associated. Because of the absence of the strong BChl c absorption found in the wild type, the bchK mutant should prove valuable for future analyses of the photosynthetic reaction center and of the roles of BChl a in photosynthesis in green bacteria. An evolutionary implication of our findings is that the photosynthetic ancestor of green sulfur bacteria could have evolved without chlorosomes and BChl c and instead used only BChl a-containing proteins as the major light-harvesting antennae.
AB - The gene encoding bacteriochlorophyll (BChl) c synthase was identified by insertional inactivation in the photosynthetic green sulfur bacterium Chlorobium tepidum and was named bchK. The bchK mutant of C. tepidum was rusty-orange in color and completely lacked BChl c. Because of the absence of the BChl c antenna, the mutant grew about seven times slower than the wild type at light intensities that were limiting to the wild type (< 90 micromol m(-2) s(-1)). Various pheophorbides, which probably represent precursors of BChl c which had lost magnesium, accumulated in the mutant cells. A small fraction of these pheophorbides were apparently esterified by the remaining chlorophyll (Chl) a and BChl a synthases in cells. The amounts of BChl a, Chl a, isoprenoid quinones, carotenoids, Fenna-Matthews-Olson protein, and chlorosome envelope protein CsmA were not significantly altered on a cellular basis in the mutant compared to in the wild type. This suggests that the BChl a antennae, photosynthetic reaction centers, and remaining chlorosome components were essentially unaffected in the mutant. Electron microscopy of thin sections revealed that the mutant lacked normal chlorosomes. However, a fraction containing vestigial chlorosomes, denoted "carotenosomes," was partly purified by density centrifugation; these structures contained carotenoids, isoprenoid quinones, and a 798-nm-absorbing BChl a species that is probably protein associated. Because of the absence of the strong BChl c absorption found in the wild type, the bchK mutant should prove valuable for future analyses of the photosynthetic reaction center and of the roles of BChl a in photosynthesis in green bacteria. An evolutionary implication of our findings is that the photosynthetic ancestor of green sulfur bacteria could have evolved without chlorosomes and BChl c and instead used only BChl a-containing proteins as the major light-harvesting antennae.
U2 - 10.1128/JB.184.12.3368-3376.2002
DO - 10.1128/JB.184.12.3368-3376.2002
M3 - Journal article
C2 - 12029054
SN - 0021-9193
VL - 184
SP - 3368
EP - 3376
JO - Journal of Bacteriology
JF - Journal of Bacteriology
IS - 12
ER -