ACT (CCP4: Supported Program)

NAME

act - analyse coordinates.

SYNOPSIS

act xyzin xyz_in.pdb
[Keyworded input]

DESCRIPTION

The program does some useful coordinate analyses. For example it quickly finds ALL the crystal contacts, no matter where the molecule is placed with respect to the origin (otherwise the fast algorithm for finding contacts is the same as in Tadeusz Skarzynski's program CONTACT).

The program always gives statistics for the temperature factors averaged by residue, for the main chain and side chains.

Lists atoms with B-values .gt. bmoni (default = 50).

Lists B-values for Ox1 and Nx2 atoms for each ASN and GLN - if the difference is large the atoms could be wrong way round.

Prints a histogram of solvent molecules in ranges of B-values.

Calculates F000 (the number of electrons in the unit cell).

The optional output includes various contact analyses.

KEYWORDED INPUT

The various data control lines are identified by keywords. Only the first 4 letters of each keyword are necessary.

BDUMP, BMONITOR, CONTACT, END (compulsory), HBOND, SEQU, SHORT, SYMM (compulsory)

SYMM <space_group name or number>

[COMPULSORY INPUT]

CONTACT <keyword> [<dmin>] <dmax>

[OPTIONAL INPUT]

Listing of contacts

   Keywords:
            ALL (default)
            INTERmolecular
            INTRAmolecular

            dmin dmax - distance limits for listing contacts,
                        in any order (default = 0.0, 5.0).
                        If only one value given it is assumed 
                        to be dmax.

SHORT <dmoni>

[OPTIONAL INPUT]

Listing of short contacts

dmoni (default = 2.5) short contacts, up to dmoni, are listed.

HBOND <keyword> <hdmin> <hdmax>

[OPTIONAL INPUT]

Listing of possible hydrogen bonds (by distance criterion). <keyword> is one of:

            ALL (default)
            INTERmolecular
            INTRAmolecular
<hdmin> <hdmax> (in any order) are the distance limits for listing contacts (default = 2.7, 3.3). A list of unpaired hydrogen bonding atoms is given with HBOND ALL option.

HBOND looks for contacts between oxygen and nitrogen atoms. An earlier version of act excluded various N/O and O/O combinations, but this was causing genuine hydrogen bonds to be missed. The current version makes no such exclusions, and therefore will list many false positives.

In any case, act uses a simple distance criterion. From the list generated, you should check:

  1. protonation: does one atom act as donor and one as acceptor? This may depend on a wider hydrogen-bonding network
  2. angles: are the bonded-donor-acceptor and donor-acceptor-bonded angles acceptable?

BMONITOR <bmoni>

[OPTIONAL INPUT]

Monitor B-values greater than bmoni (default = 50.0).

BDUMP

[OPTIONAL INPUT]

Dump ascii plot files (BRES.PLT) for the B-factors to disk

SEQU

[OPTIONAL INPUT]

Extract sequence and analyse the amino acid composition.

END

[COMPULSORY INPUT]

last card, ends input.

NOTE

PLOTTING:

If NAG graphics library is available: Uncomment the call to plotit and the ACTPLOT code and link with the library. You can then plot B-values by residue with keyword:

BPLT

[OPTIONAL INPUT]

Plot B-values by residue with NAG graphics library

INPUT AND OUTPUT FILES

The input files are:
  1. Control data file
  2. Input coordinate file in PDB format
The output files are:
  1. Listing of program output to the printer.
  2. BRES.PLT ascii plot file for the B-factors, if BDUMP keyword was read.

PRINTER OUTPUT

The printer output starts with F000 (the number of electrons in the unit cell), the number of amino acid residues, solvent molecules, metal and other atoms in the input file.

The program then outputs analysis of the temperature factors by residue for main chain and side chains. For each chain a table is printed for the distribution of residues in ranges of standard deviation of the B-values. The residues with temperature factor greater than three standard deviations from the average value are listed. This analysis is done for main chain and side chain atoms for each chain separately.

A list is given of atoms with B-values greater than bmoni, if input, or 50 by default.

Next follows a list of B-values for the oxygens and nitrogens of the amide groups of glutamines and asparagines. This can be used as a check if those atoms are placed the wrong way round - the difference would then be large.

At the end of the 'compulsory' output a histogram of the solvent molecules is given in ranges of temperature factors

For the contact searching options pairs of atoms are listed and the distance between then. If the contact is with a symmetry related atom the number of NSYM symmetry operation is given for that atom followed by the number of translations of whole unit cell along x, y and z.

For the HBOND ALL option a list of unpaired hydrogen bonding atoms is given. For well refined structures the atoms with hydrogen bonding potential should normally make a bond, perhaps with the exception of main chain nitrogens of prolines.

For SEQU option the sequence is extracted from the input file and listed for each chain in both the three-letter and one letter notations. Next the amino acid composition is listed followed by a histogram.

EXAMPLES

UNIX example script

$CEXAM/unix/runnable/act.exam
Example using toxd data.

AUTHORS

Originators : Wojtek Rypniewski and Howard Terry

SEE ALSO

Alternative B factor analysis: Alternative distance analysis: General references:
  1. W.Kabsch and C.Sander (1983) Biopolymers 22, 2577-2637
    Dictionary of Protein Secondary Structure - Pattern-recognition of hydrogen-bonded and geometrical features.