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Effects of multimerization on the temporal variability of protein complex abundance.

Häkkinen A, Tran H, Yli-Harja O, Ingalls B, Ribeiro AS - BMC Syst Biol (2013)

Bottom Line: We show that, although multimerization increases noise by reducing the mean number of functional complexes it can reduce noise in comparison with a monomer, when abundance of the functional proteins are comparable.Alternatively, reduction in noise occurs if both monomeric and multimeric forms of the protein are functional.Moreover, we find that multimerization either increases the response time to external signals or decreases the correlation between number of functional complexes and protein production kinetics.

View Article: PubMed Central - HTML - PubMed

ABSTRACT
We explore whether the process of multimerization can be used as a means to regulate noise in the abundance of functional protein complexes. Additionally, we analyze how this process affects the mean level of these functional units, response time of a gene, and temporal correlation between the numbers of expressed proteins and of the functional multimers. We show that, although multimerization increases noise by reducing the mean number of functional complexes it can reduce noise in comparison with a monomer, when abundance of the functional proteins are comparable. Alternatively, reduction in noise occurs if both monomeric and multimeric forms of the protein are functional. Moreover, we find that multimerization either increases the response time to external signals or decreases the correlation between number of functional complexes and protein production kinetics. Finally, we show that the results are in agreement with recent genome-wide assessments of cell-to-cell variability in protein numbers and of multimerization in essential and non-essential genes in Escherichia coli, and that the effects of multimerization are tangible at the level of genetic circuits.

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Change in mean levels due to heterodimerization. Relative mean levels of heterodimers P1,2 and homodimers P1,1 (with double kM to compensate for the reduction in the mean level) as a function of the mean monomer level . The inset shows linear gain.
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Figure 3: Change in mean levels due to heterodimerization. Relative mean levels of heterodimers P1,2 and homodimers P1,1 (with double kM to compensate for the reduction in the mean level) as a function of the mean monomer level . The inset shows linear gain.

Mentions: The ratio of the mean levels of the heterodimer and homodimer is plotted in Figure 3 as a function of the mean level of one of the proteins (X1, or equivalently X2). As in the homodimer case, when the mean levels is high, nearly all proteins are present in dimeric form, and so both models have the same mean abundance of functional protein, whereas for low means, there is a population of unpaired proteins which results in a reduction of the mean level of the dimer when compared to the non-dimerizing gene. Moreover, the heterodimer case exhibits greater reductions in the mean than the homodimer case, since to form a dimer, the "missing" protein has to be of a certain type.


Effects of multimerization on the temporal variability of protein complex abundance.

Häkkinen A, Tran H, Yli-Harja O, Ingalls B, Ribeiro AS - BMC Syst Biol (2013)

Change in mean levels due to heterodimerization. Relative mean levels of heterodimers P1,2 and homodimers P1,1 (with double kM to compensate for the reduction in the mean level) as a function of the mean monomer level . The inset shows linear gain.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3750523&req=5

Figure 3: Change in mean levels due to heterodimerization. Relative mean levels of heterodimers P1,2 and homodimers P1,1 (with double kM to compensate for the reduction in the mean level) as a function of the mean monomer level . The inset shows linear gain.
Mentions: The ratio of the mean levels of the heterodimer and homodimer is plotted in Figure 3 as a function of the mean level of one of the proteins (X1, or equivalently X2). As in the homodimer case, when the mean levels is high, nearly all proteins are present in dimeric form, and so both models have the same mean abundance of functional protein, whereas for low means, there is a population of unpaired proteins which results in a reduction of the mean level of the dimer when compared to the non-dimerizing gene. Moreover, the heterodimer case exhibits greater reductions in the mean than the homodimer case, since to form a dimer, the "missing" protein has to be of a certain type.

Bottom Line: We show that, although multimerization increases noise by reducing the mean number of functional complexes it can reduce noise in comparison with a monomer, when abundance of the functional proteins are comparable.Alternatively, reduction in noise occurs if both monomeric and multimeric forms of the protein are functional.Moreover, we find that multimerization either increases the response time to external signals or decreases the correlation between number of functional complexes and protein production kinetics.

View Article: PubMed Central - HTML - PubMed

ABSTRACT
We explore whether the process of multimerization can be used as a means to regulate noise in the abundance of functional protein complexes. Additionally, we analyze how this process affects the mean level of these functional units, response time of a gene, and temporal correlation between the numbers of expressed proteins and of the functional multimers. We show that, although multimerization increases noise by reducing the mean number of functional complexes it can reduce noise in comparison with a monomer, when abundance of the functional proteins are comparable. Alternatively, reduction in noise occurs if both monomeric and multimeric forms of the protein are functional. Moreover, we find that multimerization either increases the response time to external signals or decreases the correlation between number of functional complexes and protein production kinetics. Finally, we show that the results are in agreement with recent genome-wide assessments of cell-to-cell variability in protein numbers and of multimerization in essential and non-essential genes in Escherichia coli, and that the effects of multimerization are tangible at the level of genetic circuits.

Show MeSH
Related in: MedlinePlus