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Advances in Understanding Carboxysome Assembly in Prochlorococcus and Synechococcus Implicate CsoS2 as a Critical Component.

Cai F, Dou Z, Bernstein SL, Leverenz R, Williams EB, Heinhorst S, Shively J, Cannon GC, Kerfeld CA - Life (Basel) (2015)

Bottom Line: Two types of carboxysome, α and β, encapsulating form IA and form IB d-ribulose-1,5-bisphosphate carboxylase/oxygenase, respectively, differ in gene organization and associated proteins.Based on our results from bioinformatic, biophysical, genetic and biochemical approaches, including peptide array scanning for protein-protein interactions, we propose a model for CsoS2 function and its spatial location in the α-carboxysome.Analogies between the pathway for β-carboxysome biogenesis and our model for α-carboxysome assembly are discussed.

View Article: PubMed Central - PubMed

Affiliation: Department of Plant and Microbial Biology, University of California, Berkeley, CA 94720, USA. fcai@lbl.gov.

ABSTRACT
The marine Synechococcus and Prochlorococcus are the numerically dominant cyanobacteria in the ocean and important in global carbon fixation. They have evolved a CO2-concentrating-mechanism, of which the central component is the carboxysome, a self-assembling proteinaceous organelle. Two types of carboxysome, α and β, encapsulating form IA and form IB d-ribulose-1,5-bisphosphate carboxylase/oxygenase, respectively, differ in gene organization and associated proteins. In contrast to the β-carboxysome, the assembly process of the α-carboxysome is enigmatic. Moreover, an absolutely conserved α-carboxysome protein, CsoS2, is of unknown function and has proven recalcitrant to crystallization. Here, we present studies on the CsoS2 protein in three model organisms and show that CsoS2 is vital for α-carboxysome biogenesis. The primary structure of CsoS2 appears tripartite, composed of an N-terminal, middle (M)-, and C-terminal region. Repetitive motifs can be identified in the N- and M-regions. Multiple lines of evidence suggest CsoS2 is highly flexible, possibly an intrinsically disordered protein. Based on our results from bioinformatic, biophysical, genetic and biochemical approaches, including peptide array scanning for protein-protein interactions, we propose a model for CsoS2 function and its spatial location in the α-carboxysome. Analogies between the pathway for β-carboxysome biogenesis and our model for α-carboxysome assembly are discussed.

No MeSH data available.


Repetitive motifs found in the three representative CsoS2 proteins. Repetitive motif found in the N-region (cyan) and M-region (green) of MED4 (a); MIT9313 (b); and Hnea (c); CsoS2 proteins; (d) MEME motif for the N-repeats; (e) long and short form of MEME motif for the M-repeats.
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life-05-01141-f006: Repetitive motifs found in the three representative CsoS2 proteins. Repetitive motif found in the N-region (cyan) and M-region (green) of MED4 (a); MIT9313 (b); and Hnea (c); CsoS2 proteins; (d) MEME motif for the N-repeats; (e) long and short form of MEME motif for the M-repeats.

Mentions: One of the distinctive features of the primary structure of CsoS2 is sequence repeats. The M-region consists of six repeats, each composed of three units of three-amino-acid short repeats which are eight amino acids apart from each other (Figure 5 and Figure 6a–c). This observation was first reported for CsoS2 proteins from four Thiobacilli strains, including Hnea [27] (Figure 6c). Similar patterns are also evident in MED4 and MIT9313 CsoS2, as shown in Figure 6 (the three-amino-acid short repeats are shown in bold and italic). In each case, by aligning all six repeats, other features emerge. For example, all M-region repetitive patterns (M-repeat) are approximately 50 amino acids long except the third one, which is 10 amino acids shorter. Some well-conserved residues stand out: a tyrosine and a pair of cysteine residues in all except in the shorter forms.


Advances in Understanding Carboxysome Assembly in Prochlorococcus and Synechococcus Implicate CsoS2 as a Critical Component.

Cai F, Dou Z, Bernstein SL, Leverenz R, Williams EB, Heinhorst S, Shively J, Cannon GC, Kerfeld CA - Life (Basel) (2015)

Repetitive motifs found in the three representative CsoS2 proteins. Repetitive motif found in the N-region (cyan) and M-region (green) of MED4 (a); MIT9313 (b); and Hnea (c); CsoS2 proteins; (d) MEME motif for the N-repeats; (e) long and short form of MEME motif for the M-repeats.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4499774&req=5

life-05-01141-f006: Repetitive motifs found in the three representative CsoS2 proteins. Repetitive motif found in the N-region (cyan) and M-region (green) of MED4 (a); MIT9313 (b); and Hnea (c); CsoS2 proteins; (d) MEME motif for the N-repeats; (e) long and short form of MEME motif for the M-repeats.
Mentions: One of the distinctive features of the primary structure of CsoS2 is sequence repeats. The M-region consists of six repeats, each composed of three units of three-amino-acid short repeats which are eight amino acids apart from each other (Figure 5 and Figure 6a–c). This observation was first reported for CsoS2 proteins from four Thiobacilli strains, including Hnea [27] (Figure 6c). Similar patterns are also evident in MED4 and MIT9313 CsoS2, as shown in Figure 6 (the three-amino-acid short repeats are shown in bold and italic). In each case, by aligning all six repeats, other features emerge. For example, all M-region repetitive patterns (M-repeat) are approximately 50 amino acids long except the third one, which is 10 amino acids shorter. Some well-conserved residues stand out: a tyrosine and a pair of cysteine residues in all except in the shorter forms.

Bottom Line: Two types of carboxysome, α and β, encapsulating form IA and form IB d-ribulose-1,5-bisphosphate carboxylase/oxygenase, respectively, differ in gene organization and associated proteins.Based on our results from bioinformatic, biophysical, genetic and biochemical approaches, including peptide array scanning for protein-protein interactions, we propose a model for CsoS2 function and its spatial location in the α-carboxysome.Analogies between the pathway for β-carboxysome biogenesis and our model for α-carboxysome assembly are discussed.

View Article: PubMed Central - PubMed

Affiliation: Department of Plant and Microbial Biology, University of California, Berkeley, CA 94720, USA. fcai@lbl.gov.

ABSTRACT
The marine Synechococcus and Prochlorococcus are the numerically dominant cyanobacteria in the ocean and important in global carbon fixation. They have evolved a CO2-concentrating-mechanism, of which the central component is the carboxysome, a self-assembling proteinaceous organelle. Two types of carboxysome, α and β, encapsulating form IA and form IB d-ribulose-1,5-bisphosphate carboxylase/oxygenase, respectively, differ in gene organization and associated proteins. In contrast to the β-carboxysome, the assembly process of the α-carboxysome is enigmatic. Moreover, an absolutely conserved α-carboxysome protein, CsoS2, is of unknown function and has proven recalcitrant to crystallization. Here, we present studies on the CsoS2 protein in three model organisms and show that CsoS2 is vital for α-carboxysome biogenesis. The primary structure of CsoS2 appears tripartite, composed of an N-terminal, middle (M)-, and C-terminal region. Repetitive motifs can be identified in the N- and M-regions. Multiple lines of evidence suggest CsoS2 is highly flexible, possibly an intrinsically disordered protein. Based on our results from bioinformatic, biophysical, genetic and biochemical approaches, including peptide array scanning for protein-protein interactions, we propose a model for CsoS2 function and its spatial location in the α-carboxysome. Analogies between the pathway for β-carboxysome biogenesis and our model for α-carboxysome assembly are discussed.

No MeSH data available.