# REP, REPLACE

NAME
REP, REPLACE - replace selected residues
SYNOPSIS
REP
REPLACE
DESCRIPTION
Replace the selected residues, using the sequence from the main sequence buffer. At present (version 1.4), garlic is capable to replace protein residues only. Do not use this command to replace nucleic bases or hetero residues. After the replacement, the structure will need some refinement.
A residue is treated as selected if the first atom which belongs to this residue is selected. For proteins, this is typically N (nitrogen).
The main sequence buffer has to be initialized before issuing the command REPLACE. The number of residues in the main sequence buffer should be equal to the number of selected residues.
SINGLE RESIDUE REPLACEMENT
To replace a single residue, use the following commands:
select residue_sequence_number
sequence = new_residue_name
replace
Example:
sel 29
seq = ser
rep
REPLACING THE ENTIRE SEQUENCE
The command REPLACE may be used to prepare the model of some protein using the experimentally solved structure of the related protein. To replace the entire protein sequence follow these general instructions:
(1) Prepare the file with the sequence of the unsolved protein (use FASTA format).
(2) Find the related, experimentally solved protein structure.
(3) Fix insertions and deletions in the sequence of the unsolved protein.
(4) Start garlic and load the known structure.
(5) Exclude hetero residues from selection (first SEL HET, than SEL COM).
(6) If there is more than one chain restrict selection (RES chain_id/*/*/*).
(7) Load the new sequence (use the command SEQ LOAD).
(8) Replace the old sequence.
Don't forget that the number of selected residues should match the number of residues in the sequence of the unsolved protein.
TEMPLATE RESIDUES
The selected residues will be replaced with the residues from the template file. Default template file contains 20 standard residues. This file should be named residues.pdb and stored to at least one of the following directories (listed in the search order):
(1) The current working directory.
(2) $HOME/garlic (garlic subdirectory of user's home directory).
(3) /usr/local/lib/garlic (the system-wide template).
If you want to add some extra residues (like modified amino-acids) to the template file, make your own copy of the file residues.pdb and keep it either in $HOME/garlic subdirectory or in your favorite working directory. It is very easy to add residues to the template file: just copy and paste the chosen exotic residue from the PDB file where you have it to the end of garlic template file. Be sure to include hydrogen atoms! There is one more thing: be sure that your residue does not have the same residue serial number as the preceding residue. You don't have to worry about the position and the orientation of your residue.
If you don't have the file residues.pdb, click here for HTML version. It is very easy to convert this version to the plain PDB, just save it as the plain text.
NOTES
(1) The command REPLACE resets the editing mode to default (no editing).
RELATED COMMANDS
Use the command SELECT to define the residues which should be replaced and SEQUENCE to define the residues which will be used as replacement.