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PepWheel is a program to view the periodic distribution of amino acid residues in protein sequences.


HelicalWheel is an alternative to the 'statistical' approach offered by other GCG secondary prediction programs such as PepPlot. The periodic distribution of amino acids on an ideal alpha-helix can be appreciated where one is looking along the helical axis . The 3.6-residue pitch of the helix brings residues i, i+/-3, and i,+/-4 together; similarly, in a beta-sheet, residues i and i+/-2 are neighbors on the same side of the sheet.


This program was written by Rodrigo Lopez S. (E-mail:; Post: Biotechnology Centre of Oslo, PO Box 1125 Blindern, N-0317 Oslo 3, Norway).

All EGCG programs are supported by the EGCG Support Team, who can be contacted by E-mail (


Here is a session with PepWheel

  % pepwheel
   PEPWHEEL uses protein sequence data
   PEPWHEEL of what sequence ?  Sw:Mel_Apido
              Start (* 1 *) ?
              End  (* 26 *) ?


This is the plot from the example session


HelicalWheel plots a peptide sequence as a helical wheel to help you recognize amphiphilic regions. PepNet is a program to view the two-dimensional helical representation of protein sequences.


None known.


PepWheel s output displays the distribution of polar and apolar residues on opposite sides of the helix, meaning that, in a 'real' helix, polar and apolar residues should cluster together on different faces of the helical wheel. One can find amphiphilic helices even in randomly generated sequences. Flinta et al. (J. Mol. Biol. 168, 193-196 (1983)) showed that, in an 18 residue long helix, with 6 polar residues randomly distributed on the helical wheel, the probability that all 6 residues would cluster on one face is as large as 6%.


Use PepWheel with care. We do not recommend plotting more than 18 residues per turn as the interpretation of the results is then made very unclear. Choose segments of approximately 40 residues in length and step along the sequence when analysing a new protein sequence.


The input file for PepWheel is a protein sequence file.


All parameters for this program may be put on the command line. Use the option -CHEck to see the summary below and to have a chance to add things to the command line before the program executes. In the summary below, the capitalized letters in the qualifier names are the letters that you must type in order to use the parameter. Square brackets ([ and ]) enclose qualifiers or parameter values that are optional. For more information, see "Using Program Parameters" in Chapter 3, Basic Concepts: Using Programs in the GCG User's Guide.

  Minimum syntax: % pepwheel [-INfile=]Sw:mel_apido -Default
  Prompted Parameters:
  -BEGin=1 -END=221     the range of interest
  Local Data Files:
  Optional Parameters:
  -STEPs=18             residues per complete cycle wheel (18 or 7)
  -TURNs=5              turns to reach the beginning again (5 or 2)
  -CIRcles=HKR          circles on all basic residues
  -DIAmonds=DENQST      diamonds on all acidic residues
  -SQUares=ILVM         squares on all hydrophobic residues
  -NOWheel              plots residues but not the wheel spokes
  Most EGCG graphics programs accept these and other switches. See the Using
  Graphics chapter of the EGCG USERS GUIDE for descriptions.
  -DENSity=150.0        plot density in bases per 100 platen units
  -LEFTMARgin=10.0      sets the left plot margin position
  -RIGHTMARgin=140.0    sets the right plot margin position
  -BOTTOMMARgin=10.0    sets the bottom plot margin position
  -TOPMARgin=90.0       sets the top plot margin position
  -BORDer               puts a line border around the plot
  -NOBORDer             suppresses a line border
  -PAGENUMber           forces page numbering
  -NOPAGENUMber         suppresses page numbering
  -TITletext="text"     overrides the default plot title
  -NOTITletext          suppresses the plot title
  -SUBTITletext="text"  overrides the default plot subtitle
  -NOSUBTITletext       suppresses the plot subtitle
  -CHEIGHT=1.5          default plot character height
  -LINESTyle1=1         plot line style 1 (set for each line)
  -LINEPERiod1=1        plot line period 1 (set for each line)
  -LINECOLor1=0         plot line colour 1 (set for each line)
  All GCG graphics programs accept these and other switches. See the Using
  Graphics chapter of the USERS GUIDE for descriptions.
  -FIGure[=FileName]  stores plot in a file for later input to FIGURE
  -FONT=3             draws all text on the plot using font 3
  -COLor=1            draws entire plot with pen in stall 1
  -SCAle=1.2          enlarges the plot by 20 percent (zoom in)
  -XPAN=10.0          moves plot to the right 10 platen units (pan right)
  -YPAN=10.0          moves plot up 10 platen units (pan up)
  -PORtrait           rotates plot 90 degrees


The Wisconsin Package must be configured for graphics before you run any program with graphics output! If the % setplot command is available in your installation, this is the easiest way to establish your graphics configuration, but you can also use commands like % postscript that correspond to the graphics languages the Wisconsin Package supports. See Chapter 5, Using Graphics in the User's Guide for more information about configuring your process for graphics.


If you need to stop this program, use C to reset your terminal and session as gracefully as possible. Searches and comparisons write out the results from the part of the search that is complete when you use C. The graphics device should stop plotting the current page and start plotting the next page. If the current page is the last page, plotters should put the pen away and graphic terminals should return to interactive mode.


The parameters and switches listed below can be set from the command line. For more information, see "Using Program Parameters" in Chapter 3, Basic Concepts: Using Programs in the GCG User's Guide.


the number of residues per wheel until the start position is reached again. The value can be 18 (show 5 turns at a pitch of 3.6 residues per turn) or 7 (show two turns at a simplified pitch of 3.5 residues per turn).


the number of turns residues per complete turn of the wheel. The value can be 5 (show 5 turns at a pitch of 3.6 residues per turn) or 2 (show two turns at a simplified pitch of 3.5 residues per turn).


draw circles around all basic residues.


draw diamonds around all acidic residues.


draw squares around all small hydrophobic residues.


draw the residues but not the spokes of the wheel.

These options apply to all GCG graphics programs. These and many others are described in detail in Chapter 5, Using Graphics of the User's Guide.


writes the plot as a text file of plotting instructions suitable for input to the Figure program instead of drawing the plot on your plotter.


draws all text characters on the plot using Font 3 (see Appendix I) .


draws the entire plot with the pen in stall 1.

These options let you expand or reduce the plot (zoom), move it in either direction (pan), or rotate it 90 degrees (rotate).


expands the plot by 20 percent by resetting the scaling factor (normally 1.0) to 1.2 (zoom in). You can expand the axes independently with -XSCAle and -YSCAle. Numbers less than 1.0 contract the plot (zoom out).


moves the plot to the right by 30 platen units (pan right).


moves the plot up by 30 platen units (pan up).


rotates the plot 90 degrees. Usually, plots are displayed with the horizontal axis longer than the vertical (landscape). Note that plots are reduced or enlarged, depending on the platen size, to fill the page.


Flinta C., von Heijne G. and Johansson, J. (1983) "Helical sidedness and the distribution of polar residues in trans-membrane helices." J. Mol. Biol. 168, 193-196.

Printed: April 22, 1996 15:54 (1162)