Limits...
Architecture and selectivity in aquaporins: 2.5 a X-ray structure of aquaporin Z.

Savage DF, Egea PF, Robles-Colmenares Y, O'Connell JD, Stroud RM - PLoS Biol. (2003)

Bottom Line: The 2.5 A resolution structure of AqpZ suggests aquaporin selectivity results both from a steric mechanism due to pore size and from specific amino acid substitutions that regulate the preference for a hydrophobic or hydrophilic substrate.This structure provides direct evidence on the molecular mechanisms of specificity between water and glycerol in this family of channels from a single species.It is to our knowledge the first atomic resolution structure of a recombinant aquaporin and so provides a platform for combined genetic, mutational, functional, and structural determinations of the mechanisms of aquaporins and, more generally, the assembly of multimeric membrane proteins.

View Article: PubMed Central - PubMed

Affiliation: Department of Biochemistry and Biophysics, University of California School of Medicine, San Francisco, California, USA.

ABSTRACT
Aquaporins are a family of water and small molecule channels found in organisms ranging from bacteria to animals. One of these channels, the E. coli protein aquaporin Z (AqpZ), has been shown to selectively conduct only water at high rates. We have expressed, purified, crystallized, and solved the X-ray structure of AqpZ. The 2.5 A resolution structure of AqpZ suggests aquaporin selectivity results both from a steric mechanism due to pore size and from specific amino acid substitutions that regulate the preference for a hydrophobic or hydrophilic substrate. This structure provides direct evidence on the molecular mechanisms of specificity between water and glycerol in this family of channels from a single species. It is to our knowledge the first atomic resolution structure of a recombinant aquaporin and so provides a platform for combined genetic, mutational, functional, and structural determinations of the mechanisms of aquaporins and, more generally, the assembly of multimeric membrane proteins.

Show MeSH
Sequence Alignment of Aquaporins with Known StructureAlignment of GlpF, AqpZ, and AQP1 is numbered according to GlpF. Helices are shown and labeled M1–M8. Residue positions of similar chemical nature are shown in blue boxes; identical residues are shown in red.
© Copyright Policy
Related In: Results  -  Collection


getmorefigures.php?uid=PMC300682&req=5

pbio.0000072-g003: Sequence Alignment of Aquaporins with Known StructureAlignment of GlpF, AqpZ, and AQP1 is numbered according to GlpF. Helices are shown and labeled M1–M8. Residue positions of similar chemical nature are shown in blue boxes; identical residues are shown in red.

Mentions: The NPA sequences from each M1–M4 and M5–M8 domain form a constrained and interlocked junction around the quasi-2-fold axis, based on asparagine, proline, and alanine from the amino-terminal ends of M3 and M7 (Figure 3). The alanine sidechain and the proline ring make a head-to-tail, twinned, largely hydrophobically driven contact with the proline and alanine of the other domain. Each asparagine sidechain is oriented by two almost ideal hydrogen bonds. For N63(68), these bonds are one from OD1 to the NH of A65(70) and one from NH2 to the carbonyl of V185(202). Similar interactions occur at N186(203). This highly constrains and orients both asparagine sidechains to project their ND2 groups strictly into the pore, which are hydrogen-bond donors to the central water molecule.


Architecture and selectivity in aquaporins: 2.5 a X-ray structure of aquaporin Z.

Savage DF, Egea PF, Robles-Colmenares Y, O'Connell JD, Stroud RM - PLoS Biol. (2003)

Sequence Alignment of Aquaporins with Known StructureAlignment of GlpF, AqpZ, and AQP1 is numbered according to GlpF. Helices are shown and labeled M1–M8. Residue positions of similar chemical nature are shown in blue boxes; identical residues are shown in red.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC300682&req=5

pbio.0000072-g003: Sequence Alignment of Aquaporins with Known StructureAlignment of GlpF, AqpZ, and AQP1 is numbered according to GlpF. Helices are shown and labeled M1–M8. Residue positions of similar chemical nature are shown in blue boxes; identical residues are shown in red.
Mentions: The NPA sequences from each M1–M4 and M5–M8 domain form a constrained and interlocked junction around the quasi-2-fold axis, based on asparagine, proline, and alanine from the amino-terminal ends of M3 and M7 (Figure 3). The alanine sidechain and the proline ring make a head-to-tail, twinned, largely hydrophobically driven contact with the proline and alanine of the other domain. Each asparagine sidechain is oriented by two almost ideal hydrogen bonds. For N63(68), these bonds are one from OD1 to the NH of A65(70) and one from NH2 to the carbonyl of V185(202). Similar interactions occur at N186(203). This highly constrains and orients both asparagine sidechains to project their ND2 groups strictly into the pore, which are hydrogen-bond donors to the central water molecule.

Bottom Line: The 2.5 A resolution structure of AqpZ suggests aquaporin selectivity results both from a steric mechanism due to pore size and from specific amino acid substitutions that regulate the preference for a hydrophobic or hydrophilic substrate.This structure provides direct evidence on the molecular mechanisms of specificity between water and glycerol in this family of channels from a single species.It is to our knowledge the first atomic resolution structure of a recombinant aquaporin and so provides a platform for combined genetic, mutational, functional, and structural determinations of the mechanisms of aquaporins and, more generally, the assembly of multimeric membrane proteins.

View Article: PubMed Central - PubMed

Affiliation: Department of Biochemistry and Biophysics, University of California School of Medicine, San Francisco, California, USA.

ABSTRACT
Aquaporins are a family of water and small molecule channels found in organisms ranging from bacteria to animals. One of these channels, the E. coli protein aquaporin Z (AqpZ), has been shown to selectively conduct only water at high rates. We have expressed, purified, crystallized, and solved the X-ray structure of AqpZ. The 2.5 A resolution structure of AqpZ suggests aquaporin selectivity results both from a steric mechanism due to pore size and from specific amino acid substitutions that regulate the preference for a hydrophobic or hydrophilic substrate. This structure provides direct evidence on the molecular mechanisms of specificity between water and glycerol in this family of channels from a single species. It is to our knowledge the first atomic resolution structure of a recombinant aquaporin and so provides a platform for combined genetic, mutational, functional, and structural determinations of the mechanisms of aquaporins and, more generally, the assembly of multimeric membrane proteins.

Show MeSH