|  |
Program |
 |
| |
 |
General Session 3: Biological oceanography & global change |
| |
|
|
The biological roles of cadmium in the coccolithophore Emiliania huxleyi CCMP 1516
GS3-30-S
Weiying Li* , State Key Laboratory of Marine Environmental Science
Haizheng Hong, State Key Laboratory of Marine Environmental Science
Dalin Shi, State Key Laboratory of Marine Environmental Science
Presenter Email: lwy@stu.xmu.edu.cn
|
| The only known biological function of cadmium (Cd) is in diatoms to serve as a metal cofactor in Cd-carbonic anhydrase (CDCA), an enzyme involved in inorganic carbon acquisition. The coccolithophore Emiliania huxleyi has a relatively higher cellular Cd quota compared with diatoms and is known to benefit from Cd addition under Zn-limited conditions. However, E. huxleyi possess a low CA activity and does not have the cdca gene, which strongly suggests that Cd must have other unknown biological roles in the organism. In this study, we compared differentially expressed proteins of E. huxleyi CCMP 1516 cultured under Zn-limited (L-Zn), Zn-limited with Cd addition (L-Zn-Cd), and Zn-replete(H-Zn) conditions using iTRAQ approach combined with LC-ESI-MS/MS. The growth rate under L-Zn conditions declined to 50% of the rate under H-Zn conditions (0.44 vs. 0.86 d-1) and was enhanced by 35% (0.59 d-1) with the addition of Cd. Proteomic analysis showed that compared to L-Zn conditions, 10 Zn-binding proteins, such as formaldehyde dehydrogenase and those involved in nucleotide synthesis (e.g., DNA polymerase and DNA/RNA helicases), were up-regulated by 20% or more under both H-Zn and L-Zn-Cd conditions, which suggests that Cd may substitute Zn in these proteins in Zn-limited E. huxleyi. In addition, the Zn-binding 40S ribosomal protein S27 and some DnaJ-class molecular chaperones with C-terminal Zn fingers were more abundant only under L-Zn-Cd condition, indicating possible roles of Cd in these proteins. Data analysis on amino acid sequence of the differentially expressed proteins is in progress to explore potential Cd-binding sites, and further biochemical and molecular experiments are being conducted to elucidate how Cd could be utilized in Zn-limited E. huxleyi CCMP 1516. |
|
|
|
|