BMC Plant Biology
Volume 8
|
Viewing options:Associated material:Related literature:- Articles citing this article
- Other articles by authors
- Related articles/pages
Tools:Post to:
|
Abstract (provisional)
Background
In bacteria, such as Salmonella typhimurium, tryptophan is synthesized from indole-3-glycerole phosphate (IGP) by a tryptophan synthase alpha beta beta alpha heterotetramer. Plants have evolved multiple alpha (TSA) and beta (TSB) homologs, which have probably diverged in biological function and their ability of subunit interaction. There is some evidence for a tryptophan synthase (TS) complex in Arabidopsis. On the other hand maize (Zea mays) expresses the TSA-homologs BX1 and IGL that efficiently cleave IGP, independent of interaction with TSB.
Results
In order to clarify, how tryptophan is synthesized in maize, two TSA homologs, hitherto uncharacterized ZmTSA and ZmTSAlike, were functionally analyzed. ZmTSA is localized in plastids, the major site of tryptophan biosynthesis in plants. It catalyzes the tryptophan synthase alpha-reaction (cleavage of IGP), and forms a tryptophan synthase complex with ZmTSB1 in vitro. The catalytic efficiency of the alpha-reaction is strongly enhanced upon complex formation. A 160 kD tryptophan synthase complex was partially purified from maize leaves and ZmTSA was identified as native alpha-subunit of this complex by mass spectrometry. ZmTSAlike, for which no in vitro activity was detected, is localized in the cytosol. ZmTSAlike, BX1, and IGL were not detectable in the native tryptophan synthase complex in leaves.
Conclusions
It was demonstrated in vivo and in vitro that maize forms a tryptophan synthase complex and ZmTSA functions as alpha-subunit in this complex.
The complete article is available as a provisional PDF. The fully formatted PDF and HTML versions are in production.
|
| 
Research article
on Google Scholar
