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Dual targeted mitochondrial proteins are characterized by lower MTS parameters and total net charge.

Dinur-Mills M, Tal M, Pines O - PLoS ONE (2008)

Bottom Line: Mitochondrial proteins were considered dual-targeted if they were also found or predicted to be localized to the cytosol, the nucleus, the endoplasmic reticulum (ER) or the peroxisome.We found that dual localized mitochondrial proteins have i) A weaker mitochondrial targeting sequence (MitoProtII score, hydrophobic moment and number of basic residues) and ii) a lower whole-protein net charge, when compared to exclusive mitochondrial proteins.Taken together, these results establish dual targeting as a widely abundant phenomenon that should affect our concepts of gene expression and protein function.

View Article: PubMed Central - PubMed

Affiliation: Department of Molecular Biology, Hebrew University Medical School, Jerusalem, Israel.

ABSTRACT

Background: In eukaryotic cells, identical proteins can be located in different subcellular compartments (termed dual-targeted proteins).

Methodology/principal findings: We divided a reference set of mitochondrial proteins (published single gene studies) into two groups: i) Dual targeted mitochondrial proteins and ii) Exclusive mitochondrial proteins. Mitochondrial proteins were considered dual-targeted if they were also found or predicted to be localized to the cytosol, the nucleus, the endoplasmic reticulum (ER) or the peroxisome. We found that dual localized mitochondrial proteins have i) A weaker mitochondrial targeting sequence (MitoProtII score, hydrophobic moment and number of basic residues) and ii) a lower whole-protein net charge, when compared to exclusive mitochondrial proteins. We have also generated an annotation list of dual-targeted proteins within the predicted yeast mitochondrial proteome. This considerably large group of dual-localized proteins comprises approximately one quarter of the predicted mitochondrial proteome. We supported this prediction by experimental verification of a subgroup of the predicted dual targeted proteins.

Conclusions/significance: Taken together, these results establish dual targeting as a widely abundant phenomenon that should affect our concepts of gene expression and protein function. Possible relationships between the MTS/mature sequence traits and protein dual targeting are discussed.

Show MeSH
Proteins with a low net charge and low hydrophobic moment tend to be dual localized (more than exclusive mitochondrial proteins).Differences in the distribution of total net charge in dual localized (black circles) and exclusively mitochondrial (white circles) proteins with either high (>6, top panel) or low (<6, bottom panel) hydrophobic moment were analyzed using χ2 test. For proteins with a low hydrophobic moment (<6) there is a statistically significant difference between dual localized (black) and exclusively mitochondrial (white) proteins (p-value<0.02).
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pone-0002161-g004: Proteins with a low net charge and low hydrophobic moment tend to be dual localized (more than exclusive mitochondrial proteins).Differences in the distribution of total net charge in dual localized (black circles) and exclusively mitochondrial (white circles) proteins with either high (>6, top panel) or low (<6, bottom panel) hydrophobic moment were analyzed using χ2 test. For proteins with a low hydrophobic moment (<6) there is a statistically significant difference between dual localized (black) and exclusively mitochondrial (white) proteins (p-value<0.02).

Mentions: Although the strength of the MTS is a predominant feature in mitochondrial targeting, other factors also play a role in this process. The net charge of the whole protein is higher in mitochondrial proteins, even though the molecular understanding underlying this observation is lacking. It has been suggested that this may reflect an evolutionary selection on proteins to accommodate the mitochondrial matrix's higher pH [17], [18]. In this regard dual targeted proteins as one would expect have a lower net charge compared to exclusive mitochondrial proteins. Thus, not only the N-terminal targeting signal but also by the entire protein properties (such as its net charge), mediate dual targeting of mitochondrial proteins. Shown in Fig. 4 is a graphic representation that refers to total net charge, hydrophobic moment (as an indication of MTS strength) and the percent of proteins (dual or exclusive) at each value. This representation shows that proteins with a low net charge and weaker MTS tend to be dual localized (rather than exclusive mitochondrial proteins).


Dual targeted mitochondrial proteins are characterized by lower MTS parameters and total net charge.

Dinur-Mills M, Tal M, Pines O - PLoS ONE (2008)

Proteins with a low net charge and low hydrophobic moment tend to be dual localized (more than exclusive mitochondrial proteins).Differences in the distribution of total net charge in dual localized (black circles) and exclusively mitochondrial (white circles) proteins with either high (>6, top panel) or low (<6, bottom panel) hydrophobic moment were analyzed using χ2 test. For proteins with a low hydrophobic moment (<6) there is a statistically significant difference between dual localized (black) and exclusively mitochondrial (white) proteins (p-value<0.02).
© Copyright Policy
Related In: Results  -  Collection

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getmorefigures.php?uid=PMC2367453&req=5

pone-0002161-g004: Proteins with a low net charge and low hydrophobic moment tend to be dual localized (more than exclusive mitochondrial proteins).Differences in the distribution of total net charge in dual localized (black circles) and exclusively mitochondrial (white circles) proteins with either high (>6, top panel) or low (<6, bottom panel) hydrophobic moment were analyzed using χ2 test. For proteins with a low hydrophobic moment (<6) there is a statistically significant difference between dual localized (black) and exclusively mitochondrial (white) proteins (p-value<0.02).
Mentions: Although the strength of the MTS is a predominant feature in mitochondrial targeting, other factors also play a role in this process. The net charge of the whole protein is higher in mitochondrial proteins, even though the molecular understanding underlying this observation is lacking. It has been suggested that this may reflect an evolutionary selection on proteins to accommodate the mitochondrial matrix's higher pH [17], [18]. In this regard dual targeted proteins as one would expect have a lower net charge compared to exclusive mitochondrial proteins. Thus, not only the N-terminal targeting signal but also by the entire protein properties (such as its net charge), mediate dual targeting of mitochondrial proteins. Shown in Fig. 4 is a graphic representation that refers to total net charge, hydrophobic moment (as an indication of MTS strength) and the percent of proteins (dual or exclusive) at each value. This representation shows that proteins with a low net charge and weaker MTS tend to be dual localized (rather than exclusive mitochondrial proteins).

Bottom Line: Mitochondrial proteins were considered dual-targeted if they were also found or predicted to be localized to the cytosol, the nucleus, the endoplasmic reticulum (ER) or the peroxisome.We found that dual localized mitochondrial proteins have i) A weaker mitochondrial targeting sequence (MitoProtII score, hydrophobic moment and number of basic residues) and ii) a lower whole-protein net charge, when compared to exclusive mitochondrial proteins.Taken together, these results establish dual targeting as a widely abundant phenomenon that should affect our concepts of gene expression and protein function.

View Article: PubMed Central - PubMed

Affiliation: Department of Molecular Biology, Hebrew University Medical School, Jerusalem, Israel.

ABSTRACT

Background: In eukaryotic cells, identical proteins can be located in different subcellular compartments (termed dual-targeted proteins).

Methodology/principal findings: We divided a reference set of mitochondrial proteins (published single gene studies) into two groups: i) Dual targeted mitochondrial proteins and ii) Exclusive mitochondrial proteins. Mitochondrial proteins were considered dual-targeted if they were also found or predicted to be localized to the cytosol, the nucleus, the endoplasmic reticulum (ER) or the peroxisome. We found that dual localized mitochondrial proteins have i) A weaker mitochondrial targeting sequence (MitoProtII score, hydrophobic moment and number of basic residues) and ii) a lower whole-protein net charge, when compared to exclusive mitochondrial proteins. We have also generated an annotation list of dual-targeted proteins within the predicted yeast mitochondrial proteome. This considerably large group of dual-localized proteins comprises approximately one quarter of the predicted mitochondrial proteome. We supported this prediction by experimental verification of a subgroup of the predicted dual targeted proteins.

Conclusions/significance: Taken together, these results establish dual targeting as a widely abundant phenomenon that should affect our concepts of gene expression and protein function. Possible relationships between the MTS/mature sequence traits and protein dual targeting are discussed.

Show MeSH