Olisko posttranslationaalista modifikaatiota Hyp muodostuksessa?

https://www.ncbi.nlm.nih.gov/pubmed/29925588

J Biol Chem. 2018 Aug 24;293(34):13033-13043. doi: 10.1074/jbc.RA118.003518. Epub 2018 Jun 20.

Structural and functional analyses of Rubisco from arctic diatom species reveal unusual posttranslational modifications.

Valegård K¹, Andralojc PJ², Haslam RP², Pearce FG¹, Eriksen GK³, Madgwick PJ², Kristoffersen AK⁴, van Lun M¹, Klein U⁴, Eilertsen HC³, Parry MAJ², Andersson I⁵.

1

From the Department of Cell and Molecular Biology, Uppsala University, Box 596, S-751 24 Uppsala, Sweden.

2

Department of Plant Science, Rothamsted Research, Harpenden, Herts AL5 2JQ, United Kingdom.

3

the Norwegian College of Fisheries Science, Arctic University of Norway, N-9037 Tromsø, Norway, and.

4

the Department of Biosciences, University of Oslo, P.O. Box 1066, Blindern, N-0316 Oslo, Norway.

5

From the Department of Cell and Molecular Biology, Uppsala University, Box 596, S-751 24 Uppsala, Sweden, inger.andersson@icm.uu.se.

Abstract

The catalytic performance of the major CO₂-assimilating enzyme, ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco), restricts photosynthetic productivity. Natural diversity in the catalytic properties of Rubisco indicates possibilities for improvement. Oceanic phytoplankton contain some of the most efficient Rubisco enzymes, and diatoms in particular are responsible for a significant proportion of total marine primary production as well as being a major source of CO₂ sequestration in polar cold waters. Until now, the biochemical properties and three-dimensional structures of Rubisco from diatoms were unknown. Here, diatoms from arctic waters were collected, cultivated, and analyzed for their CO₂-fixing capability. We characterized the kinetic properties of five and determined the crystal structures of four Rubiscos selected for their high CO₂-fixing efficiency. The DNA sequences of the rbcL and rbcS genes of the selected diatoms were similar, reflecting their close phylogenetic relationship. The V_max and K_m for the oxygenase and carboxylase activities at 25 °C and the specificity factors (S_c/o) at 15, 25, and 35 °C were determined. The S_c/o values were high, approaching those of mono- and dicot plants, thus exhibiting good selectivity for CO₂ relative to O₂ Structurally, diatom Rubiscos belong to form I C/D, containing small subunits characterized by a short βA-βB loop and a C-terminal extension that forms a β-hairpin structure (βE-βF loop). Of note, the diatom Rubiscos featured a number of posttranslational modifications of the large subunit, including 4-hydroxyproline, β-hydroxyleucine, hydroxylated and nitrosylated cysteine, mono- and dihydroxylated lysine, and trimethylated lysine. Our studies suggest adaptation toward achieving efficient CO₂ fixation in arctic diatom Rubiscos.

© 2018 Valegård et al.

KEYWORDS:
CO2/O2 specificity; carbon fixation; crystal structure; diatoms; enzyme kinetics; posttranslational modification (PTM); ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco)

PMID:

29925588

PMCID:

PMC6109933

DOI:

10.1074/jbc.RA118.003518

[Indexed for MEDLINE]

Free PMC Article

•