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{| class="model-ib" style="float:right; margin-left:1em; margin-bottom:1em;" ! Rubisco protein abundance |- | '''Approach:''' immunodetection or targeted mass spectrometry |- | '''Context:''' ''in situ'', incubation, lab |- | '''Spatial scale:''' point sample |- | '''Tem..."

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Created page with "{{BreadcrumbsPrimaryProduction}} * Page authors: PRIMO * Responsible curator: Hagen Buck-Wiese ---- __TOC__ <div class="model-box"> {| class="model-ib" style="float:right; margin-left:1em; margin-bottom:1em;" ! Rubisco protein abundance |- | '''Approach:''' immunodetection or targeted mass spectrometry |- | '''Context:''' ''in situ'', incubation, lab |- | '''Spatial scale:''' point sample |- | '''Tem..."

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{{BreadcrumbsPrimaryProduction}}

* [[Page authors|Page authors]]: [[PRIMO]]
* [[Responsible curator|Responsible curator]]: [[User:Hagi BucknWise|Hagen Buck-Wiese]]
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<div class="model-box">
{| class="model-ib" style="float:right; margin-left:1em; margin-bottom:1em;"
! Rubisco protein abundance
|-
| '''Approach:''' immunodetection or targeted mass spectrometry
|-
| '''Context:''' ''in situ'', incubation, lab
|-
| '''Spatial scale:''' point sample
|-
| '''Temporal scale:''' minutes to hours
|-
| '''Units:''' mol protein per cell; mol protein L-1; protein mass fraction
|-
| '''Community captured:''' bulk to group-specific
|-
| '''Co-measurements:''' Single Turnover Chlorophyll Fluorescence; 14C or 13C fixation; total protein
|}
</div>
<div style="clear:both"></div>

== Method Overview ==

RuBisCO (ribulose-1,5-bisphosphate carboxylase/oxygenase) concentration is quantified in phytoplankton cell extracts or filtered field samples using immunodetection (Western blotting with antibodies raised against conserved RuBisCO epitopes) or targeted proteomics by mass spectrometry (MS). Antibody-based approaches use global antisera that recognize multiple RuBisCO forms across diverse taxa, allowing community-level estimates without prior taxonomic assignment. Targeted MS methods use selected-reaction monitoring (SRM) with synthetic peptide standards to quantify taxon-specific RuBisCO peptides, providing group-resolved Rubisco content<ref name="Young2024">Young, J. N., Rundell, S., Cooper, Z. S., Dawson, H. M., Carpenter, S. D., Ryan-Keogh, T., Rowland, E., Bertrand, E. M., & Deming, J. W. (2024). Photosynthetic processes in Antarctic sea ice during the spring melt. ''Limnology and Oceanography'', 69, 1562–1576. https://doi.org/10.1002/lno.12596</ref>.

When combined with kinetic constants for RuBisCO carboxylation and in situ temperature and CO2 concentrations, RuBisCO content can be used to model potential carbon fixation rates.

=== Scale of measurement ===

Each filtered sample provides a point measurement. Because protein turnover is slower than mRNA turnover, RuBisCO concentrations integrate the biosynthesis history over hours to days, providing a more stable signal than transcript measurements.

=== Data generated ===

RuBisCO concentrations per cell or per unit volume; when taxon-specific peptide standards are used, group-resolved estimates are obtained. Conversion to carbon fixation rates requires RuBisCO-specific kinetic constants (kcat, Km(CO2)).

=== Units & currency ===

Units are mol protein per cell, mg protein L-1, or protein mass fraction. The currency is protein (carbon fixation is a derived quantity).

=== Sample size ===

Typical samples are ~1 L in volume.

=== Repositories & databases ===

== Limitations ==

Post-translational modifications and activation states (RuBisCO requires carbamylation and Mg2+ binding for activity) affect the relationship between protein abundance and actual carboxylation rate. Peptide standards and antibodies may not capture the full diversity of RuBisCO forms (Form I vs. Form II; α vs. β subunits) across the community. Accurate total protein per liter measurements in dilute open-ocean waters are technically challenging. Models linking RuBisCO content to carbon fixation are still under active development.

== Example Applications & Protocols ==

=== Classic examples ===
* Orellana & Perry (1992) ''An immunoprobe to measure Rubisco concentrations and maximal photosynthetic rates of individual phytoplankton cells'' <ref name="Orellana1992">Orellana, M. V., & Perry, M. J. (1992). An immunoprobe to measure Rubisco concentrations and maximal photosynthetic rates of individual phytoplankton cells. ''Limnology and Oceanography'', 37(3), 478–490. https://doi.org/10.4319/lo.1992.37.3.0478</ref>
* Campbell et al. (2003) ''Analysing photosynthetic complexes in uncharacterized species or mixed microalgal communities using global antibodies'' <ref name="Campbell2003">Campbell, D. A., Cockshutt, A. M., & Porankiewicz-Asplund, J. (2003). Analysing photosynthetic complexes in uncharacterized species or mixed microalgal communities using global antibodies. ''Physiologia Plantarum'', 119(3), 322–327. https://doi.org/10.1034/j.1399-3054.2003.00175.x</ref>

=== Recent applications ===
* Young et al. (2024) ''Photosynthetic processes in Antarctic sea ice during the spring melt'' <ref name="Young2024" />
* Roberts et al. (2024) ''Rubisco in high Arctic tidewater glacier–marine systems: a new window into phytoplankton dynamics'' <ref name="Roberts2024">Roberts, M. E., Bhatia, M. P., Rowland, E., White, P. L., Waterman, S., Cavaco, M. A., Williams, P., Young, J. N., Spence, J. S., Tremblay, J.-É., Montero-Serrano, J.-C., & Bertrand, E. M. (2024). Rubisco in high Arctic tidewater glacier–marine systems: a new window into phytoplankton dynamics. ''Limnology and Oceanography'', 69, 802–817. https://doi.org/10.1002/lno.12525</ref>

=== Common calculations/conversions ===
* Potential GPP = [Rubisco] × kcat(T) × [CO2] / (Km(CO2) + [CO2]); where kcat is temperature-adjusted.

== References ==

[[Category:Main Pages|Model types]]

Rubisco protein - Revision history