An overview on the recently discovered iota-carbonic anhydrases

Figures & data

Figure 1. Multialignment of the ι-CA amino acid sequences from different species (bacteria, cyanobacteria, diatoms, and algae). In red, the putative residues of the catalytic triad (T106, Y124, S199); light blue colour, the H197 as the putative proton shuttle residue. In green are the other residues of the catalytic pocket (see Hirakawa et al. [64]). The putative motif (H)HHSS is the typical consensus sequence characterising the ι-CAs. The asterisk (*) indicates identity at all aligned positions. The multialignment was performed with MUSCLE, version 3.1. See Table 1 for the identification of the amino acid sequences used in the multialignment. The residue number system used refers to the AspCA enzyme.

Figure 2. Phylogenetic analysis of ι-CAs from various organisms. The dendrogram was constructed using the ι-CA amino acid sequences reported in Table 1.

Table 1. Organisms, acronyms, and accession numbers of the amino acid sequences used in the phylogenetic analysis of ι-CAs.

Organism	Acronym	Accession number
Anabaena sp. PCC7120	AspCA_iota_nometal	7C5V_A
Bigelowiella natans	BnaCA_iota_nometal	7C5X_A
Fistulifera solaris	FsoCA_diatom	GAX12146.1
Thalassiosira pseudonana	TpsCA_Diatom	XP_002293761.1
Thalassiosira oceanica	TocCA_diatom	EJK63051.1
Pseudo-nitzschia multistriata	PmuCA_diatom	VEU38613.1
Fragilariopsis cylindrus CCMP1102	FcyCA_diatom	OEU14464.1
Saccharothrix sp.	SacCA_bacterium	WP_053720260.1
Xanthomonas campestris	XcaCA_bacterium	WP_011036063.1
Ephemeroptericola cinctiostellae	EciCA_bacterium	WP_114562659.1
Thiotrichales bacterium	ThiCA_bacterium	OYX05505.1
Burkholderia territorii	BteCA_bacterium	WP_063553346.1
Ralstonia solanacearum	RalCA_bacterium	WP_089190700.1
Enterobacter ludwigii	EluCA_bacterium	WP_074176950.1
Kosakonia oryziphila	KorCA_bacterium	WP_090137393.1
Pragia fontium	PfoCA_bacterium	WP_047780468.
Salmonella enterica	CfrCA_bacterium	ECP0341226.1
Serratia plymuthica	SplCA_bacterium	WP_064115041.1
Buttiauxella sp.	BspCA_bacterium	WP_183271195.1
Enterobacterales	Enterobacterales_bacteria	WP_003833285.1
Salmonella enterica	SenCA_bacterium	ECP0341226.1
Klebsiella pneumoniae	KpnCA_bacterium	WP_064115041.1

Figure 3. Ribbon view of (A) hNFT2 (PDB 1GY5), (B) CAMKII in complex with acetate (PDB 2W2C), (C) AspCA (ι-CA from Anabaena cyanobacterium) in complex with HCO₃^- (PDB 7C5V), (D) BnaCA (ι-CA from microalga Bigelowiella natans) in complex with I^- (PDB 7C5Y), (E) XcaCA (ι-CA from X. campestris) in complex with putative HCO₃^- (PDB 3H51), (F) homology model of BteCA (ι-CA from B. territorii) using XcaCA as template (51% identity).

Figure 4. (A) Ribbon upper view and (B) binding site view of AspCA (ι-CA from Anabaena cyanobacterium) in complex with HCO3- (PDB 7C5V), (C) Ribbon upper view and (D) binding site view of XcaCA (ι-CA from X. campestris) in complex with putative HCO₃^- (PDB 3H51). Residue numbers according to AspCA (PDB 7C5V).

Figure 5. Binding site view of (A) AspCA (ι-CA from Anabaena cyanobacterium) in complex with HCO₃^- (PDB 7C5V), (B) BnaCA (ι-CA from microalga Bigelowiella natans) in complex with I^- (PDB 7C5Y), (C) XcaCA (ι-CA from X. campestris) in complex with putative HCO₃^- (PDB 3H51), (D) homology model of BteCA (ι-CA from B. territorii) using XcaCA as template (51% identity), (E) CAMKII in complex with acetate (PDB 2W2C). Residue numbers according to AspCA (PDB 7C5V).

Hirakawa Y, Senda M, Fukuda K, et al. Characterization of a novel type of carbonic anhydrase that acts without metal cofactors. BMC Biol 2021;19:105.

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