read.fasta.pdb: Read Aligned Structure Data

Description Usage Arguments Details Value Note Author(s) References See Also Examples

Description

Read aligned PDB structures and store their C-alpha atom data, including xyz coordinates, residue numbers, residue type and B-factors.

Usage

1
2
read.fasta.pdb(aln, prefix = "", pdbext = "", fix.ali = FALSE,
             pdblist=NULL, ncore = 1, nseg.scale = 1, ...)

Arguments

aln

an alignment data structure obtained with read.fasta.

prefix

prefix to aln$id to locate PDB files.

pdbext

the file name extention of the PDB files.

fix.ali

logical, if TRUE check consistence between $ali and $resno, and correct $ali if they don't match.

pdblist

an optional list of pdb objects with sequence corresponding to the alignments in aln. Primarily used through function pdbaln when the PDB objects already exists (avoids reading PDBs from file).

ncore

number of CPU cores used to do the calculation. ncore>1 requires package ‘parallel’ installed.

nseg.scale

split input data into specified number of segments prior to running multiple core calculation. See fit.xyz.

...

other parameters for read.pdb.

Details

The input aln, produced with read.fasta, must have identifers (i.e. sequence names) that match the PDB file names. For example the sequence corresponding to the structure “1bg2.pdb” should have the identifer ‘1bg2’. See examples below.

Sequence miss-matches will generate errors. Thus, care should be taken to ensure that the sequences in the alignment match the sequences in their associated PDB files.

Value

Returns a list of class "pdbs" with the following five components:

xyz

numeric matrix of aligned C-alpha coordinates.

resno

character matrix of aligned residue numbers.

b

numeric matrix of aligned B-factor values.

chain

character matrix of aligned chain identifiers.

id

character vector of PDB sequence/structure names.

ali

character matrix of aligned sequences.

resid

character matrix of aligned 3-letter residue names.

sse

character matrix of aligned helix and strand secondary structure elements as defined in each PDB file.

call

the matched call.

Note

The sequence character ‘X’ is useful for masking unusual or unknown residues, as it can match any other residue type.

Author(s)

Barry Grant

References

Grant, B.J. et al. (2006) Bioinformatics 22, 2695–2696.

See Also

read.fasta, read.pdb, core.find, fit.xyz, read.all, pymol.pdbs

Examples

 1
 2
 3
 4
 5
 6
 7
 8
 9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
# Redundant testing excluded

# Read sequence alignment
file <- system.file("examples/kif1a.fa",package="bio3d")
aln  <- read.fasta(file)

# Read aligned PDBs
pdbs <- read.fasta.pdb(aln)

# Structure/sequence names/ids
basename( pdbs$id )

# Alignment positions 335 to 339
pdbs$ali[,335:339]
pdbs$resid[,335:339]
pdbs$resno[,335:339]
pdbs$b[,335:339]

# Alignment C-alpha coordinates for these positions
pdbs$xyz[, atom2xyz(335:339)]

# See 'fit.xyz()' function for actual coordinate superposition
#  e.g. fit to first structure
# xyz <- fit.xyz(pdbs$xyz[1,], pdbs)
# xyz[, atom2xyz(335:339)]

bio3d documentation built on July 31, 2017, 9:01 a.m.