CAVENV (CCP4: Supported Program)

NAME

   cavenv - Visualise cavities in macromolecular structures

SYNOPSIS

   cavenv xyzin foo_in.pdb mapout foo_out.map
   [Keyworded input]

DESCRIPTION

   CAVENV produces a CCP4 map from an input model structure, which is
   designed to help visualise cavities in the protein. By default, the
   program produces a "cavity" map in which each grid point is given a
   value equal to the distance of the closest atom, minus its Van der
   Waals radius, up to a maximum of <maxrad> (maximal probe radius to
   be tested). Thus the grid values are zero within the Van der Waals
   envelope  of  the  protein.  Outside this envelope, the value
   represents radius of the largest probe that access that grid point.
   In the middle of solvent regions, the grid value is that of the
   largest probe considered <maxrad>.

   The program will also output an estimate of the percent protein and
   percent solvent in the volume covered by the generated map. Here,
   "protein" refers to the Van der Waals envelope of the atoms in the
   input model, and will include crystallographic waters unless they
   are specifically excluded. The "solvent" is the complement of the
   protein region, and thus larger than the volume accessible to the
   centre of a solvent probe. These percentages can only be compared
   to the value from a Matthews coefficient calculation if the output
   map covers a whole number of asymmetric units.

   If one of the keywords ENVPROTEIN, ENVNCS or ENVSOLVENT is given,
   then a mask is produced instead of the cavity map.

INPUT AND OUTPUT FILES

   The following input and output files are used by the program:

   Input Files:

   XYZIN
          Coordinates of model of interest. The program will generate
          symmetry mates of the input coordinates automatically.

   Output Files:

   MAPOUT
          Output map containing cavity map, or mask.

KEYWORDED INPUT

  TITLE <title string>

   Job title. Included in MAPOUT header.
   Default is "From CAVENV".

  RADMAX <maxrad> Maximum probe radius to be tested in Angstrom.
  Default is 3.0 RANGE <nfirst> <nlast>Residue range of atoms to be
  included from XYZIN. This applies to all chains.
  Default range is 1 to 10000. EXCLUDE <atomname>Atoms to be excluded
  from XYZIN, e.g. "EXCLUDE NZ". Several EXCLUDE cards may be given
  (up to a maximum number which is currently 150). CELL <a> <b> <c> [
  <alpha> <beta> <gamma> ]Input cell parameters explicitly. If
  omitted, program will try to obtain cell parameters from XYZIN. SYMM
  [<spacegroup number> | <spacegroup name> | <symmetry operations> |
  OFF]

  Input spacegroup explicitly. If omitted, program will try to obtain
  spacegroup from XYZIN.

  The spacegroup symmetry operators, together with lattice
  translations up to one unit cell in any direction, are used to
  generate symmetry mates of the atoms in XYZIN that lie within the
  limits of the output map. If the input coordinates are in a wildly
  different location from the desired map limits, then some relevant
  coordinates may not be generated.

  If the subkeyword OFF is given, then no symmetry or lattive
  translations are applied.
  AXIS <fast axis> <medium axis> <slow axis> Specify the axis order
  for the output map, where each axis is one of "X", "Y" or "Z".
  Default is "AXIS X Y Z". GRID <nx> <ny> <nz>

  Number of sampling divisions along whole cell edges.
  Default is such as to give grid spacing of 0.5 A.
  XYZLIM <xmin> <xmax> <ymin> <ymax> <zmin> <zmax>

  Range of unit cell to be included in output map. <xmin> <xmax> etc.
  are minimum and maximum grid numbers along each cell edge.
  Default is to include entire unit cell.
  ENVPROTEIN Instead of the default cavity map, MAPOUT will contain a
  protein mask with 1's within the protein region and 0's in the
  solvent region. The solvent region is defined as the volume
  accessible by a probe of radius <maxrad> (see RADMAX keyword). Thus
  the solvent region corresponds to the flat central region of the
  cavity map, when the same value of <maxrad> is used.

  ENVNCS <numncs>

   As ENVPROTEIN, but masks will be generated for <numncs> NCS-related
   molecules. This card should be followed by 3 x <numncs> records
   specifying the NCS operators. Each record consists of 3 elements of
   the rotation matrix and one element of the translation. The first
   group of three records will usually represent the identity:

1.0 0.0 0.0 0.0
0.0 1.0 0.0 0.0
0.0 0.0 1.0 0.0

  ENVSOLVENT

   Instead of the default cavity map, MAPOUT will contain a solvent
   mask with 1's within the solvent region and 0's in the protein
   region. The solvent region is defined as the volume accessible by a
   probe of radius <maxrad> (see RADMAX keyword). Thus the solvent
   region corresponds to the flat central region of the cavity map,
   when the same value of <maxrad> is used.

  END

   End of the keyword list

EXAMPLES

  Runnable examples using rnase data

     * cavenv.exam
       Simple example of producing a cavity map from the rnase model
       coordinates.

  Other examples

   [job example (unix)]

cavenv xyzin model.pdb mapout output.map << eof
range 1 2000               ! include this residue range
radmax 3.0                         ! add 3.0 Angstroem to R_vdw
TITLE probe sizes < 3 Angstroem  ! title for cavity map or envelope
CELL 100. 100. 100. 90. 90. 90.  ! unit cell (can be artificial)
AXIS X Y Z                 ! fast, medium and slow map index
GRID 200 200 200                   ! Ngrid along A/B/C for unit cell
XYZLIM 46 102 58 144 166 224     ! grid limits along A/B/C
SYMMETRY 1                         ! space group
ENVNCS 6                           ! make envelope for a hexamer
1.0 0.0 0.0 0.0            !
0.0 1.0 0.0 0.0            ! 1st ncs operation
0.0 0.0 1.0 0.0            !
-0.496382    0.868067   -0.008077          21.3054 !
-0.868089   -0.496407   -0.001331          39.5577 ! 2nd ncs operation
-0.005165    0.006350    0.999966          44.4143 !
-1.000000   -0.000038    0.000297          44.4809 !
 0.000039   -1.000000    0.000687          92.5910 ! 3rd ncs operation
 0.000297    0.000687    1.000000          66.5566 !
-0.498075   -0.867075    0.010130          44.8044 !
 0.867133   -0.498059    0.004165           1.1216 ! 4th ncs operation
 0.001434    0.010859    0.999940          88.5292 !
 0.498336    0.866924   -0.010155          -0.3177 !
-0.866981    0.498328   -0.003483          91.4965 ! 5th ncs operation
 0.002041    0.010540    0.999942          21.9734 !
 0.496579   -0.867951    0.008414          23.1853 !
 0.867971    0.496611    0.002098          53.0822 ! 6th ncs operation
-0.005999    0.006261    0.999962         110.9757 !
eof

Bugs

   The main memory requirement is holding the map in memory. The
   program is currently dimensioned to hold a maximal map size of
   3375000 (150*150*150) grid points. If this is too large for your
   system, then you need to change the value of NMAP in 1 PARAMETER
   statement in the source code, and recompile.

SEE ALSO

   areaimol - Analyse solvent accessible areas

REFERENCES

    1. A.  Volbeda,  private communication or with reference (in
       french): Anne Volbeda, Speleologie des hydrogenases a nickel et
       a fer. In: "Les Ecoles Physique et Chimie du Vivant, numero 1 -
       avril 1999, Analyse de l'organisation tridimensionnelle des
       proteines", pp 47-52.

   Other examples using CAVENV:
    1. T. I. Doukov, T. M. Iverson, J. Seravalli, S. W. Ragsdale, C.
       L. Drennan (2002) Science 298 567 - 572
       "...  putative  channel  for  CO as calculated by program
       CAVENV..."

AUTHORS

   ANNE VOLBEDA, IBS/LCCP GRENOBLE
   CCP4 version - Martyn Winn