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α(2)-µ-Globulin fragment (a2-f) from kidneys of male rats.

Hai A, Kizilbash NA - Bioinformation (2013)

Bottom Line: It is believed that unusual structural features permit A2-f to be targeted to the proximal tubule cell; to escape lysosomal degradation in liver and to enter the cytosol of proximal tubule cells of the kidneys.Homology modeling has been employed to determine the structural elements of this protein and they have been compared with the published structure of A2U.Results suggest differences between the structure of A2-f and its precursor protein A2U.

View Article: PubMed Central - PubMed

Affiliation: Department of Biochemistry, Faculty of Medicine, Northern Border University, Arar-91431, Saudi Arabia.

ABSTRACT
The structure of α(2)-µ-Globulin fragment (A2-f) is not known.α(2)-µ-Globulin fragment (A2-f) is a 15.5 kDa protein that binds equimolar amount of fatty acids in male rat kidneys. The expression of this protein has been shown to change in response to druginduced and genetic hypertension which suggests that it plays an important role in renal fatty acid metabolism under pathological conditions as well as normal conditions. A2-f has sequence homology with amino acid 28-178 of α(2)-µ-Globulin (A2U) that is synthesized pre-dominantly in the male rat liver and is present in the urine. It is believed that unusual structural features permit A2-f to be targeted to the proximal tubule cell; to escape lysosomal degradation in liver and to enter the cytosol of proximal tubule cells of the kidneys. Homology modeling has been employed to determine the structural elements of this protein and they have been compared with the published structure of A2U. Results suggest differences between the structure of A2-f and its precursor protein A2U.

No MeSH data available.


Related in: MedlinePlus

(a) Comparison of secondary structure elements of A2-f with A2U. The secondary structure elements of A2U are based onthe crystal structure of A2U; (b) Tertiary structure of A2-f obtained by homology modeling.
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Figure 1: (a) Comparison of secondary structure elements of A2-f with A2U. The secondary structure elements of A2U are based onthe crystal structure of A2U; (b) Tertiary structure of A2-f obtained by homology modeling.

Mentions: Comparison of the amino acid sequence of A2U and A2-frevealed that the difference in the number of amino acidsbetween the two proteins is thirty one. A2U has 181 aminoacids while A2-f has 150 amino acids. In A2-f, twenty eightamino acids have been omitted at the N-terminus and threeamino acids at the C-terminus. The additional amino acids inA2U at N-terminus and C-terminus are present either asrandom coil or as a bend. The homology modeling determinedtertiary structure of A2-f is typical for lipocalins (Figure 1a). It isan eight-stranded, antiparallel, symmetrical γ-barrel fold, whichis actually a γ-sheet which has been rolled into a cylindricalshape. Inside this is a ligand binding site, which plays animportant role in the transport properties of A2-f. Thesecondary structure (Figure 1b) shows that A2-f posseses fivea-helices and nine γ-strands. There are also 3 single amino acidγ-turns, 1 two amino acids γ-turn, 1 three amino acids γ-turn, 5four amino acids γ-turns, 1 five amino acids γ-turn and a singlesix amino acids γ-turn. There are three Glycine residues presentin the secondary structure elements. Gly-8 is present at thebeginning of γA; Gly-44 is present in the middle of γC and Gly-112 is at the end of γH. The rest of the Glycine residues and allof the Proline residues are present in the γ-turns. Table 1 (seesupplementary material) summarizes the ten observedstructural differences between A2-f and A2U. It shows thatthere are differences between A2-f and A2U in both the positionand length of αI, αIII, αV, γA, γB, γC, γF and γG. There is also anadditional γ-strand and 310-helix present in A2U.


α(2)-µ-Globulin fragment (a2-f) from kidneys of male rats.

Hai A, Kizilbash NA - Bioinformation (2013)

(a) Comparison of secondary structure elements of A2-f with A2U. The secondary structure elements of A2U are based onthe crystal structure of A2U; (b) Tertiary structure of A2-f obtained by homology modeling.
© Copyright Policy - open-access
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3569602&req=5

Figure 1: (a) Comparison of secondary structure elements of A2-f with A2U. The secondary structure elements of A2U are based onthe crystal structure of A2U; (b) Tertiary structure of A2-f obtained by homology modeling.
Mentions: Comparison of the amino acid sequence of A2U and A2-frevealed that the difference in the number of amino acidsbetween the two proteins is thirty one. A2U has 181 aminoacids while A2-f has 150 amino acids. In A2-f, twenty eightamino acids have been omitted at the N-terminus and threeamino acids at the C-terminus. The additional amino acids inA2U at N-terminus and C-terminus are present either asrandom coil or as a bend. The homology modeling determinedtertiary structure of A2-f is typical for lipocalins (Figure 1a). It isan eight-stranded, antiparallel, symmetrical γ-barrel fold, whichis actually a γ-sheet which has been rolled into a cylindricalshape. Inside this is a ligand binding site, which plays animportant role in the transport properties of A2-f. Thesecondary structure (Figure 1b) shows that A2-f posseses fivea-helices and nine γ-strands. There are also 3 single amino acidγ-turns, 1 two amino acids γ-turn, 1 three amino acids γ-turn, 5four amino acids γ-turns, 1 five amino acids γ-turn and a singlesix amino acids γ-turn. There are three Glycine residues presentin the secondary structure elements. Gly-8 is present at thebeginning of γA; Gly-44 is present in the middle of γC and Gly-112 is at the end of γH. The rest of the Glycine residues and allof the Proline residues are present in the γ-turns. Table 1 (seesupplementary material) summarizes the ten observedstructural differences between A2-f and A2U. It shows thatthere are differences between A2-f and A2U in both the positionand length of αI, αIII, αV, γA, γB, γC, γF and γG. There is also anadditional γ-strand and 310-helix present in A2U.

Bottom Line: It is believed that unusual structural features permit A2-f to be targeted to the proximal tubule cell; to escape lysosomal degradation in liver and to enter the cytosol of proximal tubule cells of the kidneys.Homology modeling has been employed to determine the structural elements of this protein and they have been compared with the published structure of A2U.Results suggest differences between the structure of A2-f and its precursor protein A2U.

View Article: PubMed Central - PubMed

Affiliation: Department of Biochemistry, Faculty of Medicine, Northern Border University, Arar-91431, Saudi Arabia.

ABSTRACT
The structure of α(2)-µ-Globulin fragment (A2-f) is not known.α(2)-µ-Globulin fragment (A2-f) is a 15.5 kDa protein that binds equimolar amount of fatty acids in male rat kidneys. The expression of this protein has been shown to change in response to druginduced and genetic hypertension which suggests that it plays an important role in renal fatty acid metabolism under pathological conditions as well as normal conditions. A2-f has sequence homology with amino acid 28-178 of α(2)-µ-Globulin (A2U) that is synthesized pre-dominantly in the male rat liver and is present in the urine. It is believed that unusual structural features permit A2-f to be targeted to the proximal tubule cell; to escape lysosomal degradation in liver and to enter the cytosol of proximal tubule cells of the kidneys. Homology modeling has been employed to determine the structural elements of this protein and they have been compared with the published structure of A2U. Results suggest differences between the structure of A2-f and its precursor protein A2U.

No MeSH data available.


Related in: MedlinePlus