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Functional Characterization of the FNT Family Nitrite Transporter of Marine Picocyanobacteria.

Maeda S, Murakami A, Ito H, Tanaka A, Omata T - Life (Basel) (2015)

Bottom Line: A strongly conserved hydrophilic amino acid sequence was found at the C-termini of the deduced NitM sequences from α-cyanobacteria, with a notable exception of the Synechococcus sp. strain CC9605 NitM protein, which entirely lacked the C-terminal amino acids.The C-terminal sequence was not conserved in the NitM proteins from β-cyanobacteria carrying the Type 1b RuBisCO, including the one from Synechococcus sp. strain PCC7002.Expression of the truncated nitM genes from Synechococcus sp. strain CC9311 and Prochlorococcus marinus strain MIT9313, encoding the proteins lacking the conserved C-terminal region, conferred nitrite uptake activity on the NA4 mutant, indicating that the C-terminal region of α-cyanobacterial NitM proteins inhibits the activity of the transporter.

View Article: PubMed Central - PubMed

Affiliation: Graduate School of Bioagricultural Sciences, Nagoya University, Nagoya 464-8601, Japan. maeda@agr.nagoya-u.ac.jp.

ABSTRACT
Many of the cyanobacterial species found in marine and saline environments have a gene encoding a putative nitrite transporter of the formate/nitrite transporter (FNT) family. The presumed function of the gene (designated nitM) was confirmed by functional expression of the gene from the coastal marine species Synechococcus sp. strain PCC7002 in the nitrite-transport-less mutant (NA4) of the freshwater cyanobacterium Synechococcus elongatus strain PCC7942. The NitM-mediated nitrite uptake showed an apparent Km (NO2-) of about 8 μM and was not inhibited by nitrate, cyanate or formate. Of the nitM orthologs from the three oceanic cyanobacterial species, which are classified as α-cyanobacteria on the basis of the occurrence of Type 1a RuBisCO, the one from Synechococcus sp. strain CC9605 conferred nitrite uptake activity on NA4, but those from Synechococcus sp. strain CC9311 and Prochlorococcus marinus strain MIT9313 did not. A strongly conserved hydrophilic amino acid sequence was found at the C-termini of the deduced NitM sequences from α-cyanobacteria, with a notable exception of the Synechococcus sp. strain CC9605 NitM protein, which entirely lacked the C-terminal amino acids. The C-terminal sequence was not conserved in the NitM proteins from β-cyanobacteria carrying the Type 1b RuBisCO, including the one from Synechococcus sp. strain PCC7002. Expression of the truncated nitM genes from Synechococcus sp. strain CC9311 and Prochlorococcus marinus strain MIT9313, encoding the proteins lacking the conserved C-terminal region, conferred nitrite uptake activity on the NA4 mutant, indicating that the C-terminal region of α-cyanobacterial NitM proteins inhibits the activity of the transporter.

No MeSH data available.


Related in: MedlinePlus

Alignment of the amino acid sequences of the C-terminal region of the cyanobacterial NitM proteins and the NAR1 protein from Chlamydomonas reinhardtii. Positively and negatively charged amino acid residues are indicated by blue and red characters, respectively. The Box indicates the sixth predicted transmembrane region. The source organisms are same as Figure 1. Asterisks indicate the amino acid residues common to all the NitM protein sequences. Dots indicate the amino acid residues common to all the α-cyanobacterial NitM proteins but the one from Synechococcus sp. strain CC9605. Dashes indicate gaps introduced to enhance the alignment.
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life-05-00432-f005: Alignment of the amino acid sequences of the C-terminal region of the cyanobacterial NitM proteins and the NAR1 protein from Chlamydomonas reinhardtii. Positively and negatively charged amino acid residues are indicated by blue and red characters, respectively. The Box indicates the sixth predicted transmembrane region. The source organisms are same as Figure 1. Asterisks indicate the amino acid residues common to all the NitM protein sequences. Dots indicate the amino acid residues common to all the α-cyanobacterial NitM proteins but the one from Synechococcus sp. strain CC9605. Dashes indicate gaps introduced to enhance the alignment.

Mentions: Among the four NitM proteins functionally characterized above, those from Synechococcus sp. strains CC9605 and CC9311 showed the strongest similarity to each other, being 82% identical to each other. The only prominent difference between the two sequences was that NitM of strain CC9605 was shorter by 20 amino acids than that of strain CC9311. Comparison of all the NitM sequences available in GenBank showed that all the NitM proteins of α-cyanobacteria, excluding the one from Synechococcus sp. strain CC9605, have a highly conserved amino acid segment at the C-terminus, which is characterized by a very high content of charged amino acids (Figure 5). The corresponding region of the NitM proteins of β-cyanobacteria, including the one from Synechococcus sp. strain PCC 7002, showed no sequence conservation. These findings suggested that the presence or absence of the conserved C-terminal segment might have determined the functionally of the NitM proteins in the NA4 cells.


Functional Characterization of the FNT Family Nitrite Transporter of Marine Picocyanobacteria.

Maeda S, Murakami A, Ito H, Tanaka A, Omata T - Life (Basel) (2015)

Alignment of the amino acid sequences of the C-terminal region of the cyanobacterial NitM proteins and the NAR1 protein from Chlamydomonas reinhardtii. Positively and negatively charged amino acid residues are indicated by blue and red characters, respectively. The Box indicates the sixth predicted transmembrane region. The source organisms are same as Figure 1. Asterisks indicate the amino acid residues common to all the NitM protein sequences. Dots indicate the amino acid residues common to all the α-cyanobacterial NitM proteins but the one from Synechococcus sp. strain CC9605. Dashes indicate gaps introduced to enhance the alignment.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4390861&req=5

life-05-00432-f005: Alignment of the amino acid sequences of the C-terminal region of the cyanobacterial NitM proteins and the NAR1 protein from Chlamydomonas reinhardtii. Positively and negatively charged amino acid residues are indicated by blue and red characters, respectively. The Box indicates the sixth predicted transmembrane region. The source organisms are same as Figure 1. Asterisks indicate the amino acid residues common to all the NitM protein sequences. Dots indicate the amino acid residues common to all the α-cyanobacterial NitM proteins but the one from Synechococcus sp. strain CC9605. Dashes indicate gaps introduced to enhance the alignment.
Mentions: Among the four NitM proteins functionally characterized above, those from Synechococcus sp. strains CC9605 and CC9311 showed the strongest similarity to each other, being 82% identical to each other. The only prominent difference between the two sequences was that NitM of strain CC9605 was shorter by 20 amino acids than that of strain CC9311. Comparison of all the NitM sequences available in GenBank showed that all the NitM proteins of α-cyanobacteria, excluding the one from Synechococcus sp. strain CC9605, have a highly conserved amino acid segment at the C-terminus, which is characterized by a very high content of charged amino acids (Figure 5). The corresponding region of the NitM proteins of β-cyanobacteria, including the one from Synechococcus sp. strain PCC 7002, showed no sequence conservation. These findings suggested that the presence or absence of the conserved C-terminal segment might have determined the functionally of the NitM proteins in the NA4 cells.

Bottom Line: A strongly conserved hydrophilic amino acid sequence was found at the C-termini of the deduced NitM sequences from α-cyanobacteria, with a notable exception of the Synechococcus sp. strain CC9605 NitM protein, which entirely lacked the C-terminal amino acids.The C-terminal sequence was not conserved in the NitM proteins from β-cyanobacteria carrying the Type 1b RuBisCO, including the one from Synechococcus sp. strain PCC7002.Expression of the truncated nitM genes from Synechococcus sp. strain CC9311 and Prochlorococcus marinus strain MIT9313, encoding the proteins lacking the conserved C-terminal region, conferred nitrite uptake activity on the NA4 mutant, indicating that the C-terminal region of α-cyanobacterial NitM proteins inhibits the activity of the transporter.

View Article: PubMed Central - PubMed

Affiliation: Graduate School of Bioagricultural Sciences, Nagoya University, Nagoya 464-8601, Japan. maeda@agr.nagoya-u.ac.jp.

ABSTRACT
Many of the cyanobacterial species found in marine and saline environments have a gene encoding a putative nitrite transporter of the formate/nitrite transporter (FNT) family. The presumed function of the gene (designated nitM) was confirmed by functional expression of the gene from the coastal marine species Synechococcus sp. strain PCC7002 in the nitrite-transport-less mutant (NA4) of the freshwater cyanobacterium Synechococcus elongatus strain PCC7942. The NitM-mediated nitrite uptake showed an apparent Km (NO2-) of about 8 μM and was not inhibited by nitrate, cyanate or formate. Of the nitM orthologs from the three oceanic cyanobacterial species, which are classified as α-cyanobacteria on the basis of the occurrence of Type 1a RuBisCO, the one from Synechococcus sp. strain CC9605 conferred nitrite uptake activity on NA4, but those from Synechococcus sp. strain CC9311 and Prochlorococcus marinus strain MIT9313 did not. A strongly conserved hydrophilic amino acid sequence was found at the C-termini of the deduced NitM sequences from α-cyanobacteria, with a notable exception of the Synechococcus sp. strain CC9605 NitM protein, which entirely lacked the C-terminal amino acids. The C-terminal sequence was not conserved in the NitM proteins from β-cyanobacteria carrying the Type 1b RuBisCO, including the one from Synechococcus sp. strain PCC7002. Expression of the truncated nitM genes from Synechococcus sp. strain CC9311 and Prochlorococcus marinus strain MIT9313, encoding the proteins lacking the conserved C-terminal region, conferred nitrite uptake activity on the NA4 mutant, indicating that the C-terminal region of α-cyanobacterial NitM proteins inhibits the activity of the transporter.

No MeSH data available.


Related in: MedlinePlus