Color By Mutations

This script creates an alignment of two proteins and superimposes them. Aligned residues that are different in the two (i.e. mutations) are highlighted and colored according to their difference in the BLOSUM90 matrix. It is meant to be used for similar proteins, e.g. close homologs or point mutants, to visualize their differences.

Example

color_by_mutation protein1, protein2

Example: rat trypsin and cow trypsin colored by color_by_mutation.

'''
created by Christoph Malisi.

Creates an alignment of two proteins and superimposes them. 
Aligned residues that are different in the two (i.e. mutations) are highlighted and 
colored according to their difference in the BLOSUM90 matrix. 
Is meant to be used for similar proteins, e.g. close homologs or point mutants, 
to visualize their differences.

'''

from pymol import cmd

aa_3l = {'ALA':0, 'ARG':1, 'ASN':2, 'ASP':3, 'CYS':4, 'GLN':5, 'GLU':6, 'GLY':7, 'HIS':8, 'ILE':9, 'LEU':10, 'LYS':11,
        'MET':12, 'PHE':13, 'PRO':14, 'SER':15, 'THR':16, 'TRP':17, 'TYR':18, 'VAL':19, 'B':20, 'Z':21, 'X':22, '*':23}

#            A   R   N   D   C   Q   E   G   H   I   L   K   M   F   P   S   T   W   Y   V   B   Z   X   *
blosum90 = [[ 5, -2, -2, -3, -1, -1, -1,  0, -2, -2, -2, -1, -2, -3, -1,  1,  0, -4, -3, -1, -2, -1, -1, -6], 
            [-2,  6, -1, -3, -5,  1, -1, -3,  0, -4, -3,  2, -2, -4, -3, -1, -2, -4, -3, -3, -2,  0, -2, -6], 
            [-2, -1,  7,  1, -4,  0, -1, -1,  0, -4, -4,  0, -3, -4, -3,  0,  0, -5, -3, -4,  4, -1, -2, -6], 
            [-3, -3,  1,  7, -5, -1,  1, -2, -2, -5, -5, -1, -4, -5, -3, -1, -2, -6, -4, -5,  4,  0, -2, -6], 
            [-1, -5, -4, -5,  9, -4, -6, -4, -5, -2, -2, -4, -2, -3, -4, -2, -2, -4, -4, -2, -4, -5, -3, -6], 
            [-1,  1,  0, -1, -4,  7,  2, -3,  1, -4, -3,  1,  0, -4, -2, -1, -1, -3, -3, -3, -1,  4, -1, -6], 
            [-1, -1, -1,  1, -6,  2,  6, -3, -1, -4, -4,  0, -3, -5, -2, -1, -1, -5, -4, -3,  0,  4, -2, -6], 
            [ 0, -3, -1, -2, -4, -3, -3,  6, -3, -5, -5, -2, -4, -5, -3, -1, -3, -4, -5, -5, -2, -3, -2, -6], 
            [-2,  0,  0, -2, -5,  1, -1, -3,  8, -4, -4, -1, -3, -2, -3, -2, -2, -3,  1, -4, -1,  0, -2, -6], 
            [-2, -4, -4, -5, -2, -4, -4, -5, -4,  5,  1, -4,  1, -1, -4, -3, -1, -4, -2,  3, -5, -4, -2, -6], 
            [-2, -3, -4, -5, -2, -3, -4, -5, -4,  1,  5, -3,  2,  0, -4, -3, -2, -3, -2,  0, -5, -4, -2, -6], 
            [-1,  2,  0, -1, -4,  1,  0, -2, -1, -4, -3,  6, -2, -4, -2, -1, -1, -5, -3, -3, -1,  1, -1, -6], 
            [-2, -2, -3, -4, -2,  0, -3, -4, -3,  1,  2, -2,  7, -1, -3, -2, -1, -2, -2,  0, -4, -2, -1, -6], 
            [-3, -4, -4, -5, -3, -4, -5, -5, -2, -1,  0, -4, -1,  7, -4, -3, -3,  0,  3, -2, -4, -4, -2, -6], 
            [-1, -3, -3, -3, -4, -2, -2, -3, -3, -4, -4, -2, -3, -4,  8, -2, -2, -5, -4, -3, -3, -2, -2, -6], 
            [ 1, -1,  0, -1, -2, -1, -1, -1, -2, -3, -3, -1, -2, -3, -2,  5,  1, -4, -3, -2,  0, -1, -1, -6], 
            [ 0, -2,  0, -2, -2, -1, -1, -3, -2, -1, -2, -1, -1, -3, -2,  1,  6, -4, -2, -1, -1, -1, -1, -6], 
            [-4, -4, -5, -6, -4, -3, -5, -4, -3, -4, -3, -5, -2,  0, -5, -4, -4, 11,  2, -3, -6, -4, -3, -6], 
            [-3, -3, -3, -4, -4, -3, -4, -5,  1, -2, -2, -3, -2,  3, -4, -3, -2,  2,  8, -3, -4, -3, -2, -6], 
            [-1, -3, -4, -5, -2, -3, -3, -5, -4,  3,  0, -3,  0, -2, -3, -2, -1, -3, -3,  5, -4, -3, -2, -6], 
            [-2, -2,  4,  4, -4, -1,  0, -2, -1, -5, -5, -1, -4, -4, -3,  0, -1, -6, -4, -4,  4,  0, -2, -6], 
            [-1,  0, -1,  0, -5,  4,  4, -3,  0, -4, -4,  1, -2, -4, -2, -1, -1, -4, -3, -3,  0,  4, -1, -6], 
            [-1, -2, -2, -2, -3, -1, -2, -2, -2, -2, -2, -1, -1, -2, -2, -1, -1, -3, -2, -2, -2, -1, -2, -6], 
            [-6, -6, -6, -6, -6, -6, -6, -6, -6, -6, -6, -6, -6, -6, -6, -6, -6, -6, -6, -6, -6, -6, -6,  1]] 

def getBlosum90ColorName(aa1, aa2):
    '''returns a rgb color name of a color that represents the similarity of the two residues according to
       the BLOSUM90 matrix. the color is on a spectrum from blue to red, where blue is very similar, and 
       red very disimilar.'''
    # return red for residues that are not part of the 20 amino acids
    if aa1 not in aa_3l or aa2 not in aa_3l:
	return 'red'
    
    # if the two are the same, return blue
    if aa1 == aa2:
	return 'blue'
    i1 = aa_3l[aa1]
    i2 = aa_3l[aa2]
    b = blosum90[i1][i2]

    # 3 is the highest score for non-identical substitutions, so substract 4 to get into range [-10, -1]
    b = abs(b - 4)

    # map to (0, 1]:
    b = 1. - (b / 10.0)

    # red = [1.0, 0.0, 0.0], blue = [0.0, 0.0, 1.0]
    colvec = [(0., 0., 1.), (1.,0.,0.)]
    bcolor = (1.-b, 0., b)
    col_name = '0x%02x%02x%02x'%(bcolor[0]*255, bcolor[1]*255, bcolor[2]*255)
    return col_name

def color_by_mutation(obj1, obj2, waters=0, labels=0):
    '''
    DESCRIPTION
    
        Creates an alignment of two proteins and superimposes them. 
        Aligned residues that are different in the two (i.e. mutations) are highlighted and 
        colored according to their difference in the BLOSUM90 matrix. 
        Is meant to be used for similar proteins, e.g. close homologs or point mutants, 
        to visualize their differences.      
    
    USAGE
    
        color_by_mutation selection1, selection2 [,waters [,labels ]]
        
    ARGUMENTS
    
        obj1: object or selection
        
        obj2: object or selection    
        
        waters: bool (0 or 1). If 1, waters are included in the view, colored
                differently for the both input structures.
                default = 0

        labels: bool (0 or 1). If 1, the possibly mutated sidechains are 
                labeled by their chain, name and id
                default = 0
        
    EXAMPLE
        
        color_by_mutation protein1, protein2
        
    SEE ALSO

        super
    '''
    from pymol import stored, CmdException

    if cmd.count_atoms(obj1) == 0:
        print '%s is empty'%obj1
        return
    if cmd.count_atoms(obj2) == 0:
        print '%s is empty'%obj2
        return
    waters = int(waters)
    labels = int(labels)
    
    # align the two proteins
    aln = '__aln'
    
    # first, an alignment with 0 cycles (no atoms are rejected, which maximized the number of aligned residues)
    # for some mutations in the same protein this works fine). This is essentially done to get a
    # sequence alignment
    cmd.super(obj1, obj2, object=aln, cycles=0)
    
    # superimpose the the object using the default parameters to get a slightly better superimposition,
    # i.e. get the best structural alignment    
    cmd.super(obj1, obj2)

    stored.resn1, stored.resn2 = [], []
    stored.resi1, stored.resi2 = [], []
    stored.chain1, stored.chain2 = [], []
    
    # store residue ids, residue names and chains of aligned residues
    cmd.iterate(obj1 + ' and name CA and ' + aln, 'stored.resn1.append(resn)')
    cmd.iterate(obj2 + ' and name CA and ' + aln, 'stored.resn2.append(resn)')

    cmd.iterate(obj1 + ' and name CA and ' + aln, 'stored.resi1.append(resi)')
    cmd.iterate(obj2 + ' and name CA and ' + aln, 'stored.resi2.append(resi)')

    cmd.iterate(obj1 + ' and name CA and ' + aln, 'stored.chain1.append(chain)')
    cmd.iterate(obj2 + ' and name CA and ' + aln, 'stored.chain2.append(chain)')
    
    
    mutant_selection = '' 
    non_mutant_selection = 'none or '
    colors = []

    # loop over the aligned residues
    for n1, n2, i1, i2, c1, c2 in zip(stored.resn1, stored.resn2,
                                      stored.resi1, stored.resi2,
                                      stored.chain1, stored.chain2):
        # take care of 'empty' chain names
        if c1 == '':
            c1 = '""'
        if c2 == '':
            c2 = '""'
        if n1 == n2:
            non_mutant_selection += '((%s and resi %s and chain %s) or (%s and resi %s and chain %s)) or '%(obj1, i1, c1, obj2, i2, c2 )            
        else:
            mutant_selection += '((%s and resi %s and chain %s) or (%s and resi %s and chain %s)) or '%(obj1, i1, c1, obj2, i2, c2 )
            # get the similarity (according to the blosum matrix) of the two residues and
            c = getBlosum90ColorName(n1, n2)
            colors.append((c, '%s and resi %s and chain %s and elem C'%(obj2, i2, c2)))

    if mutant_selection == '':
        print ' Error: No mutations found'
        raise CmdException

    # create selections        
    cmd.select('mutations', mutant_selection[:-4])
    cmd.select('non_mutations', non_mutant_selection[:-4])
    cmd.select('not_aligned', '(%s or %s) and not mutations and not non_mutations'%(obj1, obj2))
    
    # create the view and coloring
    cmd.hide('everything', '%s or %s'%(obj1, obj2))
    cmd.show('cartoon', '%s or %s'%(obj1, obj2))
    cmd.show('lines', '(%s or %s) and ((non_mutations or not_aligned) and not name c+o+n)'%(obj1, obj2))
    cmd.show('sticks', '(%s or %s) and mutations and not name c+o+n'%(obj1, obj2))
    cmd.color('gray', 'elem C and not_aligned')
    cmd.color('white', 'elem C and non_mutations')
    cmd.color('blue', 'elem C and mutations and %s'%obj1)
    for (col, sel) in colors:
        cmd.color(col, sel)

    cmd.hide('everything', '(hydro) and (%s or %s)'%(obj1, obj2))        
    cmd.center('%s or %s'%(obj1, obj2))
    if labels:
        cmd.label('mutations and name CA','"(%s-%s-%s)"%(chain, resi, resn)')    
    if waters:
        cmd.set('sphere_scale', '0.1')
        cmd.show('spheres', 'resn HOH and (%s or %s)'%(obj1, obj2))
        cmd.color('red', 'resn HOH and %s'%obj1)
        cmd.color('salmon', 'resn HOH and %s'%obj2)
    print '''
             Mutations are highlighted in blue and red.
             All mutated sidechains of %s are colored blue, the corresponding ones from %s are
             colored on a spectrum from blue to red according to how similar the two amino acids are
             (as measured by the BLOSUM90 substitution matrix).
             Aligned regions without mutations are colored white.
             Regions not used for the alignment are gray.
             NOTE: There could be mutations in the gray regions that were not detected.'''%(obj1, obj2)
    cmd.delete(aln)
    cmd.deselect()
    

    
cmd.extend("color_by_mutation", color_by_mutation)