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Molecular evolution of multiple arylalkylamine N-acetyltransferase (AANAT) in fish.

Zilberman-Peled B, Bransburg-Zabary S, Klein DC, Gothilf Y - Mar Drugs (2011)

Bottom Line: Multiple aanats are present in teleost fish as a result of whole genome and gene duplications.These results suggest that substrate selectivity of AANAT1a and AANAT2 is determined by the positioning of the substrate within the catalytic pocket, and its accessibility to catalysis.This illustrates the evolutionary process by which enzymes encoded by duplicated genes acquire different activities and play different biological roles.

View Article: PubMed Central - PubMed

Affiliation: Department of Neurobiology, George S. Wise Faculty of Life Sciences, Tel Aviv University, Tel Aviv 69978, Israel.

ABSTRACT
Arylalkylamine N-acetyltransferase (AANAT) catalyzes the transfer of an acetyl group from acetyl coenzyme A (AcCoA) to arylalkylamines, including indolethylamines and phenylethylamines. Multiple aanats are present in teleost fish as a result of whole genome and gene duplications. Fish aanat1a and aanat2 paralogs display different patterns of tissue expression and encode proteins with different substrate preference: AANAT1a is expressed in the retina, and acetylates both indolethylamines and phenylethylamines; while AANAT2 is expressed in the pineal gland, and preferentially acetylates indolethylamines. The two enzymes are therefore thought to serve different roles. Here, the molecular changes that led to their specialization were studied by investigating the structure-function relationships of AANATs in the gilthead seabream (sb, Sperus aurata). Acetylation activity of reciprocal mutated enzymes pointed to specific residues that contribute to substrate specificity of the enzymes. Inhibition tests followed by complementary analyses of the predicted three-dimensional models of the enzymes, suggested that both phenylethylamines and indolethylamines bind to the catalytic pocket of both enzymes. These results suggest that substrate selectivity of AANAT1a and AANAT2 is determined by the positioning of the substrate within the catalytic pocket, and its accessibility to catalysis. This illustrates the evolutionary process by which enzymes encoded by duplicated genes acquire different activities and play different biological roles.

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3-D surface properties of the catalytic funnel of seabream AANAT1a and AANAT2. The 3-D models of AANAT1a (left panels) and AANAT2 (right panels) were reconstructed based on the 3-D structure of the sheep AANAT complex with a bisubstrate analog [15]. The curvature analysis of the surface is shown on the upper part of the picture, with the innermost regions colored in grey and the outermost in green (see scale bar). The lower part of the picture depicts the electrostatic properties analysis of the funnel, with the positive parts colored in blue and the negative parts in red (see scale bar). Residues that form the amine binding site and catalytic residues are colored as follows: Phe51(AANAT1a) and Phe54 (AANAT2), red; Pro59 (AANAT1a) and Pro62 (AANAT2), yellow; Met154 (AANAT1a) and Ile157 (AANAT2), magenta; Val178 (AANAT1a) and Ile181 (AANAT2), green; Leu181 (AANAT1a) and Met184 (AANAT2), blue; His115 (AANAT1a) and His118 (AANAT2), cyan; His117 (AANAT1a) and His120 (AANAT2), grey. Grasp software package was used for the surface property analysis.
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f4-marinedrugs-09-00906: 3-D surface properties of the catalytic funnel of seabream AANAT1a and AANAT2. The 3-D models of AANAT1a (left panels) and AANAT2 (right panels) were reconstructed based on the 3-D structure of the sheep AANAT complex with a bisubstrate analog [15]. The curvature analysis of the surface is shown on the upper part of the picture, with the innermost regions colored in grey and the outermost in green (see scale bar). The lower part of the picture depicts the electrostatic properties analysis of the funnel, with the positive parts colored in blue and the negative parts in red (see scale bar). Residues that form the amine binding site and catalytic residues are colored as follows: Phe51(AANAT1a) and Phe54 (AANAT2), red; Pro59 (AANAT1a) and Pro62 (AANAT2), yellow; Met154 (AANAT1a) and Ile157 (AANAT2), magenta; Val178 (AANAT1a) and Ile181 (AANAT2), green; Leu181 (AANAT1a) and Met184 (AANAT2), blue; His115 (AANAT1a) and His118 (AANAT2), cyan; His117 (AANAT1a) and His120 (AANAT2), grey. Grasp software package was used for the surface property analysis.

Mentions: Structural analysis. Since phenylethylamines appear to bind to the catalytic pocket of AANAT2, it may be hypothesized that the kinetic differences and substrate preferences between the two enzymes stem from differences in the spatial relationships between the bound substrate and catalytic residues. This hypothesis was further explored by investigating the predicted 3-D structures of the seabream AANAT1a and AANAT2, using the structure of the sheep AANAT-bisubstrate analog complex PDB accession number: 1CJW [15] as a template. General surface and electrostatic properties were evaluated to assess the similarities and differences between the catalytic funnels of the two enzymes. Figure 4 depicts the curvature analysis of the surface (upper panels), and the electrostatic properties analysis (lower panels) of the catalytic funnel of AANAT1a and AANAT2. The overall topology of the funnel in the AANAT1a and AANAT2 models is fairly similar, with some minor differences. One stems from the presence of Leu181vs. Met184 in AANAT1a and AANAT2, respectively. The longer side chain of the Met184 (colored blue) projects to the cavity (lower part of the pocket), and covers part of Ile181 of AANAT2 (colored green). It should be noted however that the Leu181 to Met184 and the Val178 to Ile181 changes have been found only in seabream AANATs, not in other known AANATs. Another topological difference, in the vicinity of the catalytic histidine residues (His115 and His117 in AANAT1a, His118 and His120 in AANAT2), is an enlargement of the cavity in AANAT2 as compared to that of AANAT1a (upper part of the cavity, Figure 4). In addition, the charge distribution between the two histidines and in the vicinity of Met154 (AANAT1a) and Ile157 (AANAT2) is different.


Molecular evolution of multiple arylalkylamine N-acetyltransferase (AANAT) in fish.

Zilberman-Peled B, Bransburg-Zabary S, Klein DC, Gothilf Y - Mar Drugs (2011)

3-D surface properties of the catalytic funnel of seabream AANAT1a and AANAT2. The 3-D models of AANAT1a (left panels) and AANAT2 (right panels) were reconstructed based on the 3-D structure of the sheep AANAT complex with a bisubstrate analog [15]. The curvature analysis of the surface is shown on the upper part of the picture, with the innermost regions colored in grey and the outermost in green (see scale bar). The lower part of the picture depicts the electrostatic properties analysis of the funnel, with the positive parts colored in blue and the negative parts in red (see scale bar). Residues that form the amine binding site and catalytic residues are colored as follows: Phe51(AANAT1a) and Phe54 (AANAT2), red; Pro59 (AANAT1a) and Pro62 (AANAT2), yellow; Met154 (AANAT1a) and Ile157 (AANAT2), magenta; Val178 (AANAT1a) and Ile181 (AANAT2), green; Leu181 (AANAT1a) and Met184 (AANAT2), blue; His115 (AANAT1a) and His118 (AANAT2), cyan; His117 (AANAT1a) and His120 (AANAT2), grey. Grasp software package was used for the surface property analysis.
© Copyright Policy - open-access
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC3111191&req=5

f4-marinedrugs-09-00906: 3-D surface properties of the catalytic funnel of seabream AANAT1a and AANAT2. The 3-D models of AANAT1a (left panels) and AANAT2 (right panels) were reconstructed based on the 3-D structure of the sheep AANAT complex with a bisubstrate analog [15]. The curvature analysis of the surface is shown on the upper part of the picture, with the innermost regions colored in grey and the outermost in green (see scale bar). The lower part of the picture depicts the electrostatic properties analysis of the funnel, with the positive parts colored in blue and the negative parts in red (see scale bar). Residues that form the amine binding site and catalytic residues are colored as follows: Phe51(AANAT1a) and Phe54 (AANAT2), red; Pro59 (AANAT1a) and Pro62 (AANAT2), yellow; Met154 (AANAT1a) and Ile157 (AANAT2), magenta; Val178 (AANAT1a) and Ile181 (AANAT2), green; Leu181 (AANAT1a) and Met184 (AANAT2), blue; His115 (AANAT1a) and His118 (AANAT2), cyan; His117 (AANAT1a) and His120 (AANAT2), grey. Grasp software package was used for the surface property analysis.
Mentions: Structural analysis. Since phenylethylamines appear to bind to the catalytic pocket of AANAT2, it may be hypothesized that the kinetic differences and substrate preferences between the two enzymes stem from differences in the spatial relationships between the bound substrate and catalytic residues. This hypothesis was further explored by investigating the predicted 3-D structures of the seabream AANAT1a and AANAT2, using the structure of the sheep AANAT-bisubstrate analog complex PDB accession number: 1CJW [15] as a template. General surface and electrostatic properties were evaluated to assess the similarities and differences between the catalytic funnels of the two enzymes. Figure 4 depicts the curvature analysis of the surface (upper panels), and the electrostatic properties analysis (lower panels) of the catalytic funnel of AANAT1a and AANAT2. The overall topology of the funnel in the AANAT1a and AANAT2 models is fairly similar, with some minor differences. One stems from the presence of Leu181vs. Met184 in AANAT1a and AANAT2, respectively. The longer side chain of the Met184 (colored blue) projects to the cavity (lower part of the pocket), and covers part of Ile181 of AANAT2 (colored green). It should be noted however that the Leu181 to Met184 and the Val178 to Ile181 changes have been found only in seabream AANATs, not in other known AANATs. Another topological difference, in the vicinity of the catalytic histidine residues (His115 and His117 in AANAT1a, His118 and His120 in AANAT2), is an enlargement of the cavity in AANAT2 as compared to that of AANAT1a (upper part of the cavity, Figure 4). In addition, the charge distribution between the two histidines and in the vicinity of Met154 (AANAT1a) and Ile157 (AANAT2) is different.

Bottom Line: Multiple aanats are present in teleost fish as a result of whole genome and gene duplications.These results suggest that substrate selectivity of AANAT1a and AANAT2 is determined by the positioning of the substrate within the catalytic pocket, and its accessibility to catalysis.This illustrates the evolutionary process by which enzymes encoded by duplicated genes acquire different activities and play different biological roles.

View Article: PubMed Central - PubMed

Affiliation: Department of Neurobiology, George S. Wise Faculty of Life Sciences, Tel Aviv University, Tel Aviv 69978, Israel.

ABSTRACT
Arylalkylamine N-acetyltransferase (AANAT) catalyzes the transfer of an acetyl group from acetyl coenzyme A (AcCoA) to arylalkylamines, including indolethylamines and phenylethylamines. Multiple aanats are present in teleost fish as a result of whole genome and gene duplications. Fish aanat1a and aanat2 paralogs display different patterns of tissue expression and encode proteins with different substrate preference: AANAT1a is expressed in the retina, and acetylates both indolethylamines and phenylethylamines; while AANAT2 is expressed in the pineal gland, and preferentially acetylates indolethylamines. The two enzymes are therefore thought to serve different roles. Here, the molecular changes that led to their specialization were studied by investigating the structure-function relationships of AANATs in the gilthead seabream (sb, Sperus aurata). Acetylation activity of reciprocal mutated enzymes pointed to specific residues that contribute to substrate specificity of the enzymes. Inhibition tests followed by complementary analyses of the predicted three-dimensional models of the enzymes, suggested that both phenylethylamines and indolethylamines bind to the catalytic pocket of both enzymes. These results suggest that substrate selectivity of AANAT1a and AANAT2 is determined by the positioning of the substrate within the catalytic pocket, and its accessibility to catalysis. This illustrates the evolutionary process by which enzymes encoded by duplicated genes acquire different activities and play different biological roles.

Show MeSH