RmsdByResidue

Type	Python Script
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Author(s)	Zhenting Gao
License

Introduction

RMSD between two structures of the same protein. The concept is similar as RMSF between two structures.

• programming
  • Platform
    • PyMOL
      • rms_cur
  • Feature
    • Output
      • RMSD of all atoms of each residues pairs
      • Least RMSD of all atoms of each residues pairs
        • symmetry of Phe, Tyr, His, Asp, Glu, Gln, Asn, Arg, Leu and Val needs to be considered
          • switch the atom name and then calculate the RMSD again
          • Selected least RMSD of a residue pair for report
            • RMSD of backbone atoms of each residues pairs
            • RMSD of C alpha atoms of each residues pairs
        • With defined residues pairs
          • Residue pair can be limited to within binding site
  • Workflow
    • Read reference and target pdb files
      • two structures should be superposed before using this function
• Note
  • Python
  • PyMOL
    • Clean attributes
      • otherwise rms_cur will fail
    • How to get residue name?
      • residue name, residue index and etc. can only be read from an atom
• Reference
  • https://sourceforge.net/p/pymol/mailman/message/32710889/

Usage

• Open PyMOL
• Load PDB files
• run this Python script inside PyMOL
• call the function
  • rmsdByRes pdb1, resSelection, pdb2

Required Arguments

Text

Optional Arguments

Text

Examples

Text

The Code

#load library
from pymol import cmd, stored
import sys
import os

#function to judge if a file exists
def is_non_zero_file(fpath):
    return os.path.isfile(fpath) and os.path.getsize(fpath) > 0

#function to switch atom names within a residue
def switchName(residueSelection, atomName1, atomName2):
  """
  switch the name of two atoms
  """
  cmd.alter(residueSelection+" and name "+atomName1, 'name="gzt"')
  cmd.alter(residueSelection+" and name "+atomName2, 'name="'+atomName1+'"')
  cmd.alter(residueSelection+" and name gzt", 'name="'+atomName2+'"')


#function to change atom names of some residues with symetric sidechain
def flipAtomName(targetResidueSelection):
  """
  switch the atom names of specific residues
  """
# Create flipped residue
  cmd.create("flippedRes",targetResidueSelection+" and not alt B")
  targetResidueCa=cmd.get_model("flippedRes and name CA")
  for g in targetResidueCa.atom:
#   print g.resn
    if g.resn=='ARG':
     switchName("flippedRes", "NH1", "NH2")
    elif g.resn=='HIS':
     switchName("flippedRes", "ND1", "CD2")
     switchName("flippedRes", "CE1", "NE2")
    elif g.resn=='ASP':
     switchName("flippedRes", "OD1", "OD2")
    elif g.resn=='PHE':
     switchName("flippedRes", "CD1", "CD2")
     switchName("flippedRes", "CE1", "CE2")
    elif g.resn=='GLN':
     switchName("flippedRes", "OE1", "NE2")
    elif g.resn=='GLU':
     switchName("flippedRes", "OE1", "OE2")
    elif g.resn=='LEU':
     switchName("flippedRes", "CD1", "CD2")
    elif g.resn=='ASN':
     switchName("flippedRes", "OD1", "ND2")
    elif g.resn=='TYR':
     switchName("flippedRes", "CD1", "CD2")
     switchName("flippedRes", "CE1", "CE2")
    elif g.resn=='VAL':
      switchName("flippedRes", "CG1", "CG2")
  cmd.sort()
# cmd.label("flippedRes","name")
  return "flippedRes"

  

#main function
def rmsdByRes(referenceProteinChain,sel, targetProteinChain):
  """
  Update
    Zhenting Gao on 7/28/2016

  USAGE

    rmsf referenceProteinChain, targetProteinChain, selection [,byres=0], [reference_state=1]

    Calculate the RMSD for each residue pairs from two chains of the same protein from two crystal structures.

  Workflow
    Read reference and target pdb files
    Align two structures
        sel target, proA and chain A
            #define target protein chain
        sel refrence, proB and chain A
            #define reference protein chain
        align target, reference
            #automatical alignment
    Clean attributes
        otherwise rms_cur will fail


  """
# Create temporary objects, exclude alternative conformation B
  cmd.create("ref_gzt", referenceProteinChain+" and polymer and not alt B")
  cmd.alter("ref_gzt", "chain='A'")
  cmd.alter("ref_gzt", "segi=''")
  cmd.create("target_gzt", targetProteinChain+" and polymer and not alt B")
  cmd.alter("target_gzt", "chain='A'")
  cmd.alter("target_gzt", "segi=''")
#  cmd.align("target_gzt","ref_gzt",object="align")
# parameters
  outputText=""
  res2Check=['HIS','ASP','ARG','PHE','GLN','GLU','LEU','ASN','TYR','VAL']
       
# select alpha carbon of selected residues in reference structure
  calpha=cmd.get_model(sel+" and name CA and not alt B")
  
  for g in calpha.atom:
#  print g.resi+g.resn
   if cmd.count_atoms("ref_gzt and polymer and resi "+g.resi)==cmd.count_atoms("target_gzt and polymer and resi "+g.resi):
    rmsdRes=cmd.rms_cur("ref_gzt and polymer and resi "+g.resi,"target_gzt and polymer and resi "+g.resi)
    rmsdResCa=cmd.rms_cur("ref_gzt and polymer and resi "+g.resi+" and name ca","target_gzt and polymer and resi "+g.resi+" and name ca")
    rmsdResBackbone=cmd.rms_cur("ref_gzt and polymer and resi "+g.resi+" and name ca+n+c+o","target_gzt and polymer and resi "+g.resi+" and name ca+n+c+o")
#  calculate minimum rmsd
    rmsdResMin=rmsdRes
    if g.resn in res2Check:
      flippedRes=flipAtomName("target_gzt and polymer and resi "+g.resi)
      rmsdFlippedRes=cmd.rms_cur("ref_gzt and polymer and resi "+g.resi,flippedRes)
      if rmsdFlippedRes<rmsdRes:
       rmsdResMin=rmsdFlippedRes

#    print cmd.count_atoms("ref_gzt and polymer and resi "+g.resi),cmd.count_atoms("target_gzt and polymer and resi "+g.resi)
    outputText+="%s,%s,%s,%.3f,%.3f,%.3f,%.3f\n" % (targetProteinChain,g.resn,g.resi,rmsdRes,rmsdResCa,rmsdResBackbone,rmsdResMin)
  
  print outputText
# Destroy temporary objects
  cmd.delete("ref_gzt target_gzt align res_gzt "+flippedRes)
  
# Save data into csv
  outputFile='rmsdByRes_'+sel+'.csv'
  f=open(outputFile,'a')
  if not is_non_zero_file(outputFile):
   f.write("targe,residueName,residueId,allAtomRMSD,rmsdResCa,rmsdResBackbone,allAtomRMSDMin\n")
  f.write(outputText)
  f.close()
  print "Results saved in "+outputFile
  
cmd.extend("rmsdByRes",rmsdByRes)