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| − | == Introduction ==
| + | [[Image:cealign_ex1.png|300px|thumb|right|cealign superposition of 1c0mB and 1bco]] |
| − | This script is a Python implementation of the CE algorithm pioneered by Drs. Shindyalov and Bourne (See References). It is a fast, accurate structure-based protein alignment algorithm. There are a few changes from the original code (See Notes), and "fast" depends on your machine and the implementation. That is, on my machine --- a relatively fast 64-bit machine --- I can align two 400+ amino acid structures in about 0.300 s with the C++ implementation. In Python however, two 165 amino acid proteins took about 35 seconds!
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| − | When coupled to the Kabsch algorithm, this should be able to align any two protein structures, using just the alpha carbon coordinates.
| + | [[cealign]] aligns two proteins using the CE algorithm. It is very robust for proteins with little to no sequence similarity (twilight zone). For proteins with decent structural similarity, the [[super]] command is preferred and with decent sequence similarity, the [[align]] command is preferred, because these commands are much faster than [[cealign]]. |
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| − | This plugs into PyMol very easily. See [[Cealign#The_Code|the code]] and [[Cealign#Examples|examples]] for installation and usage. | + | ''This command is new in PyMOL 1.3, see the [[cealign plugin]] for manual installation.'' |
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| − | == Comparison to PyMol == | + | == Usage == |
| − | '''Why should you use this?'''
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| − | PyMol's structure alignment algorithm is fast and robust. However, its first step is to perform a sequence alignment of the two selections. Thus, proteins in the '''twilight zone''' or those having a low sequence identity, may not align well. Because CE is a structure-based alignment, this is not a problem. Look at the following example. The image at LEFT was the result of CE-aligning two proteins (1C0M to 1BCO). The result is '''88''' aligned (alpha carbons) residues (not atoms) at '''2.78 Angstroms'''. The image on the RIGHT shows the results from PyMol's align command: an alignment of '''221 atoms''' (not residues) at an RMSD of '''15.7 Angstroms'''. To make the alignment easier to see, cealign (actually the [[Kabsch]] code) colors the aligned residues differently.
| + | cealign target, mobile [, target_state [, mobile_state |
| | + | [, quiet [, guide [, d0 [, d1 [, window [, gap_max |
| | + | [, transform [, object ]]]]]]]]]] |
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| − | <gallery>
| + | == Arguments == |
| − | Image:Ce_works.png|Cealign's results
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| − | Image:Pymol_align.png|PyMol's results
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| − | </gallery>
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| | + | '''Note''': The '''mobile''' and '''target''' arguments are swapped with respect to the [[align]] and [[super]] commands. |
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| − | == Examples == | + | * '''target''' = string: atom selection of target object |
| − | === Usage === | + | * '''mobile''' = string: atom selection of mobile object |
| − | <source lang="python">
| + | * '''target_state''' = int: object state of target selection {default: 1} |
| − | cealign 1cll and i. 42-55, 1ggz and c. A
| + | * '''mobile_state''' = int: object state of mobile selection {default: 1} |
| − | cealign 1kao, 1ctq
| + | * '''quiet''' = 0/1: suppress output {default: 0 in command mode, 1 in API} |
| − | cealign 1fao, 1eaz
| + | * '''guide''' = 0/1: only use "guide" atoms (CA, C4') {default: 1} |
| − | </source>
| + | * '''d0, d1, window, gap_max''': CE algorithm parameters |
| | + | * '''transform''' = 0/1: do superposition {default: 1} |
| | + | * '''object''' = string: name of alignment object to create {default: (no alignment object)} |
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| − | === Results === | + | == Example == |
| − | <gallery>
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| − | Image:Cealign1.png|EASY: 1FAO vs. 1EAZ; 88 residues, 1.16 Ang
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| − | Image:Cealign2.png|EASY: 1CBS vs. 1HMT; 120 residues, 2.07 Ang
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| − | Image:Cealign3.png|MODERATE: 1A15 vs 1B50; 56 residues, 6.67 Ang.
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| − | Image:Align.png|EASY: 1OAN vs. 1S6N; aligned to 2.26 Ang. RMSD.
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| − | Image:Cealign_ex_hard.png|HARD: 1RLW to 1BYN; 104 residues; 3.94 Ang.
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| − | Image:1ten_3hhr.png|HARD: 1TEN vs. 3HHR; 72 residues, 3.13 Ang.
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| − | Image:2SIM_1NSB.png|HARD: 2SIM vs. 1NSB; 280 residues, 5.00 Ang.
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| − | Image:1CEW_1MOL.png|HARD: 1CEW vs. 1MOL; 72 residues, 3.63 Ang.
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| − | </gallery>
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| | | | |
| − | == Installation == | + | <syntaxhighlight lang="python"> |
| | + | fetch 1c0mB 1bco, async=0 |
| | + | as ribbon |
| | + | cealign 1bco, 1c0mB, object=aln |
| | + | </syntaxhighlight> |
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| − | '''note:''' Windows installer coming soon.
| + | == See Also == |
| | | | |
| − | ===Requirements===
| + | * [[super]] |
| − | # Numpy
| + | * [[align]] |
| − | # Python 2.4+ with distutils
| + | * [[cealign plugin]] |
| − | # C compiler
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| | | | |
| − | ===Directions===
| + | [[Category:Commands|Align]] |
| − | # uncompress the distribution file '''cealign-VERSION.tgz'''
| + | [[Category:Structure_Alignment|Align]] |
| − | # cd cealign-VERSION
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| − | # sudo python setup.py install
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| − | # insert "run DIR_TO_CEALIGN/cealign.py" and "run DIR_TO_CEALIGN/qkabsch.py" into your '''.pymolrc''' file, or just run the two Python scripts by hand.
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| − | # load some molecules
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| − | # run, '''cealign molecule1, molecule2'''
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| − | # enjoy
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| − | | |
| − | == The Code ==
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| − | Please unpack and read the documentation. All comments/questions should be directed to Jason Vertrees (javertre _at_ utmb ...dot... edu)
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| − | | |
| − | === Version 0.1 ===
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| − | * BZ2 File [http://www.pymolwiki.org/images/a/a9/Cealign-0.1.tar.bz2 CE Align v0.1]
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| − | * ZIP File [http://www.pymolwiki.org/images/0/0c/Cealign-0.1.zip CE Align v0.1]
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| − | | |
| − | == Updates ==
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| − | ===2007-01-17===
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| − | CE Align V0.1 released.
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| − | | |
| − | ===2007-01-11===
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| − | The first version of the C-module code is complete. I fixed handling (multiple) missing residues, the centering problem, and the problem of multiple chains. I'll package and provide the code soon.
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| − | | |
| − | ===2007-01-10===
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| − | Trying to remedy missing residues. If a user's selections are '''protA and i. 10-20''' and '''prot2 and i. 10-20''', and if prot2 is missing residue 14, the SVD is undefined/inappropriate. I have to weed out residues that don't have partners in the PDB file. Alignments do this implicitly since the XYZ values it sees are only the ones with coordinates. Also, CE only works on individual chains. If someone can find a consistent method to map residues and chains to ints and then back to residues and chains -- that might work. Ha!
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| − | If more than a week lapses after this comment, I'll just wrap up the code and post the first version. There seems to be some interest in this plugin, so the more eyes the easier it may be to fix the bugs. I will also need testers for the Mac and Windows editions.
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| − | | |
| − | === 2007-01-08===
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| − | '''Yeah!'''
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| − | The C code that plugs into PyMol has been completed. It's a little slower than the plain C++ code I wrote, but that's what you get when passing data from PyMol to Python to C, fiddle with it, pass it back to Python to PyMol for some more quick math. The alignment times for the two proteins mentioned below (1B50 and 1C0M) on my machine with the new C module is about 1-3 second (with a full CPU load for other intensive tasks running in the background; this shows great improvement over the pure Python alignment times). Once the code is cleaned up (and I'm not too embarrassed to post it) and some bugs are worked out, I'll post it. The current bugs are:
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| − | # Some alignments don't center right
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| − | # Missing residues cause problems
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| − | # Memory leaks galore, I'm sure
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| − | | |
| − | The code consists of:
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| − | * qkabsch.py
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| − | * cealign.py
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| − | * ccealignmodule.c
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| − | * ccealignmodule.h
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| − | * setup.py
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| − | | |
| − | Also, I provide the option of aligning based solely upon RMSD or upon the better CE-Score. See the '''References''' for information on the '''CE Score'''.
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| − | | |
| − | == Troubleshooting ==
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| − | Post your problems/solutions here.
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| − | | |
| − | === LinAlg Module Not Found ===
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| − | '''Problem''': Running CE Align gives the following error message:
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| − | <source lang="python">
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| − | run qkabsch.py
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| − | Traceback (most recent call last):
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| − | File "/usr/lib/python2.4/site-packages/pymol/parser.py", line 285, in parse
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| − | parsing.run_file(exp_path(args[nest][0]),pymol_names,pymol_names)
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| − | File "/usr/lib/python2.4/site-packages/pymol/parsing.py", line 407, in run_file
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| − | execfile(file,global_ns,local_ns)
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| − | File "qkabsch.py", line 86, in ?
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| − | import numpy
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| − | File "/usr/lib/python2.4/site-packages/numpy/__init__.py", line 40, in ?
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| − | import linalg
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| − | ImportError: No module named linalg
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| − | </source>
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| − | '''Solution''': You do not have the linear algebra module installed (or Python can't find it) on your machine. One workaround is to install [http://www.scipy.org/ Scientific Python]. Another is to reinstall the Numpy package from source, ensuring that you have the necessary requirements for the linear algebra module (linpack, lapack, fft, etc.).
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| − | === NumPy Module Not Found ===
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| − | '''Problem''': Running CE Align gives the following error message:
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| − | <source lang="python">
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| − | run qkabsch.py
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| − | Traceback (most recent call last):
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| − | File "/home/local/warren/MacPyMOL060530/build/Deployment/MacPyMOL.app/pymol/modules/pymol/parser.py", line 297, in parse
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| − | File "/home/local/warren/MacPyMOL060530/build/Deployment/MacPyMOL.app/pymol/modules/pymol/parsing.py", line 408, in run_file
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| − | File "qkabsch.py", line 86, in ?
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| − | import numpy
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| − | ImportError: No module named numpy
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| − | </source>
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| − | '''Solution''': This problem occurs under Apple Mac OS X if (a) you are using the sponsorised version of PyMOL (MacPyMOL/PyMOLX11Hybrid) and (b) the Apple's python executable on your machine (/usr/bin/python, currently version 2.3.5) is superseded by Fink's python executable (/sw/bin/python, currently version 2.5). MacPyMOL/PyMOLX11Hybrid ignores Fink's python, and will only use Apple's - so, in order to run CE Align, one must install NumPy using Apple's python. To do so, download the [http://sourceforge.net/project/showfiles.php?group_id=1369&package_id=175103 Numpy source code], unpack it and specify the full path to Apple's python executable during installation: <tt>/usr/bin/python setup.py install</tt>.
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| − | [[User:Lucajovine|Luca Jovine]] 05:11, 25 January 2007 (CST) | |
| − | | |
| − | == References ==
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| − | Text taken from PubMed and formatted for the wiki. The first reference is the most important for this code.
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| − | # Shindyalov IN, Bourne PE. '''Protein structure alignment by incremental combinatorial extension (CE) of the optimal path.''' ''Protein Eng.'' 1998 Sep;11(9):739-47. PMID: 9796821 [PubMed - indexed for MEDLINE]
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| − | # Jia Y, Dewey TG, Shindyalov IN, Bourne PE. '''A new scoring function and associated statistical significance for structure alignment by CE.''' ''J Comput Biol.'' 2004;11(5):787-99. PMID: 15700402 [PubMed - indexed for MEDLINE]
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| − | # Pekurovsky D, Shindyalov IN, Bourne PE. '''A case study of high-throughput biological data processing on parallel platforms.''' ''Bioinformatics.'' 2004 Aug 12;20(12):1940-7. Epub 2004 Mar 25. PMID: 15044237 [PubMed - indexed for MEDLINE]
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| − | # Shindyalov IN, Bourne PE. '''An alternative view of protein fold space.''' ''Proteins.'' 2000 Feb 15;38(3):247-60. PMID: 10713986 [PubMed - indexed for MEDLINE]
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| − | == License ==
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| − | The CEAlign and all its subprograms that I wrote, are released under the open source Free BSD License (BSDL).
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