System and methods for predicting transmembrane domains in membrane proteins and mining the genome for recognizing G-protein coupled receptors
The invention provides computer-implemented methods and apparatus implementing a hierarchical protocol using multiscale molecular dynamics and molecular modeling methods to predict the presence of transmembrane regions in proteins, such as G-Protein Coupled Receptors (GPCR), and protein structural models generated according to the protocol. The protocol features a coarse grain sampling method, such as hydrophobicity analysis, to provide a fast and accurate procedure for predicting transmembrane regions. Methods and apparatus of the invention are useful to screen protein or polynucleotide databases for encoded proteins with transmembrane regions, such as GPCRs.
1. A method for predicting the transmembrane (TM) region(s) of a TM protein, comprising:
(1) obtaining amino acid sequence and/or sequence alignment for said TM protein;
(2) plotting a hydrophobic profile using a specifically programmed computing device, and using said amino acid sequence and/or sequence alignment; and
(3) assigning / identifying initial TM regions based on the global average hydrophobicity of said amino acid sequence and/or said sequence alignment, and a base_mod within 0.05 thereof;
thereby predicting TM region(s) for said TM protein.
2. The method of claim 1 , further comprising:
(4) capping each initial TM regions identified in (3) to yield capped TM regions, based on the presence of helix breakers.
3. The method of claim 1 , wherein said hydrophobic profile is based on at least a portion of said TM protein.
4. The method of claim 3 , wherein said portion excludes one or more of: the N- or C-terminal region(s) not in contact with lipid bilayers, or inter-TM region loops.
5. The method of claim 1 , wherein said hydrophobic profile uses peak signal analysis.
6. The method of claim 5 , wherein said hydrophobic profile is generated by the SeqHyd profile algorithm.
7. The method of claim 6 , comprising:
(1) obtaining amino acid sequence and sequence alignment for said TM protein by:
(a) using the sequence of said protein as query, retrieving from a database an ensemble of hit sequences with 20-90% sequence identity, and/or BLAST bit score >200 and E-value >e −100 ;
(b) obtaining a multisequence alignment of said hit sequences and the sequence of said protein; and
(c) calculating consensus hydrophobicity for every residue position in said alignment;
(2) plotting said hydrophobic profile based on said consensus hydrophobicity; and
(3) assigning initial TM regions based on the global average hydrophobicity of said alignment, and a base_mod within 0.05 thereof.
8. The method of claim 7 , further comprising:
(4) capping each initial TM regions identified in (3) to yield capped TM regions, based on the presence of helix breakers.
9. The method of claim 7 , wherein (3) further comprises identifying additional TM helix region(s) with peak length <23 and peak area <0.8, using local average hydrophobicity more than 0.05 less than said base_mod, if said additional TM helix region(s) are not identified based either on said global average hydrophobicity or said base_mod.
10. The method of claim 7 , wherein said capped TM regions exclude N- and C-terminal helix breakers.
11. The method of claim 6 , wherein said hydrophobic profile is based alone on the amino acid sequence of said protein.
12. The method of claim 11 , comprising:
(1) obtaining amino acid sequence for said TM protein;
(2) plotting said hydrophobic profile based on the hydrophobicity of each residue within said amino acid sequence; and
(3) assigning / identifying initial TM regions based on the global average hydrophobicity of said amino acid sequence alignment, and a base_mod within 0.05 thereof.
13. The method of claim 12 , further comprising:
(4) capping each initial TM regions identified in (3) to yield capped TM regions, based on the presence of helix breakers.
14. A non-transitory computer readable storage medium having a computer executable software code stored therein, which code, upon execution, carries out a method for predicting the transmembrane (TM) region(s) of a TM protein, said method comprising:
(1) obtaining amino acid sequence and/or sequence alignment for said TM protein;
(2) plotting a hydrophobic profile using said amino acid sequence and/or sequence alignment; and
(3) assigning / identifying initial TM regions based on the global average hydrophobicity of said amino acid sequence and/or said sequence alignment, and a base_mod within 0.05 thereof;
thereby predicting TM region(s) for said TM protein.
15. A computer hardware system for predicting the transmembrane (TM) region(s) of a TM protein, comprising:
(1) a data input hardware module device for obtaining amino acid sequence and/or sequence alignment for said TM protein;
(2) a profile generation hardware module device for plotting a hydrophobic profile using said amino acid sequence and/or sequence alignment; and
(3) a TM region identification hardware module device for assigning / identifying initial TM regions based on the global average hydrophobicity of said amino acid sequence and/or said sequence alignment, and a base_mod within 0.05 thereof.