Services
TMHMM - 2.0
Prediction of transmembrane helices in proteins
NOTE: TMHMM-2.0 is outdated. A more recent and better transmembrane predictor, DeepTMHMM, has been released and is available at https://services.healthtech.dtu.dk/service.php?DeepTMHMM. |
Submission
Restrictions:
At most 10,000 sequences and 4,000,000 amino acids per submission; each sequence not more than 8,000 amino acids.
Confidentiality:
The sequences are kept confidential and will be deleted after processing.
TMHMM-2.0 Guide
This server is for prediction of transmembrane helices in proteins.
July 2001: TMHMM has been rated best in an independent comparison of programs for prediction of TM helices:
- S. Moller, M.D.R. Croning, R. Apweiler.
Evaluation of methods for the prediction of membrane spanning regions.
Bioinformatics, 17(7):646-653, July 2001. (medline)
`Our results show that TMHMM is currently the best performing transmembrane prediction program.'
TMHMM is described in
- A. Krogh,
B. Larsson, G. von Heijne, and E. L. L. Sonnhammer.
Predicting transmembrane protein topology with a hidden Markov model: Application to complete genomes.
Journal of Molecular Biology, 305(3):567-580, January 2001.
(PDF, 959503 bytes) - E. L.L.
Sonnhammer, G. von Heijne, and A. Krogh.
A hidden Markov model for predicting transmembrane helices in protein sequences.
In J. Glasgow, T. Littlejohn, F. Major, R. Lathrop, D. Sankoff, and C. Sensen, editors, Proceedings of the Sixth International Conference on Intelligent Systems for Molecular Biology, pages 175-182, Menlo Park, CA, 1998. AAAI Press.
(Gzipped PostScript, 8 pages, 42470 bytes) (PDF, 844205 bytes)
Please cite.
Press here to see other material (training data, etc).
Input
The program takes proteins in FASTA format. It recognizes the 20 amino acids and B, Z, and X, which are all treated equally as unknown. Any other character is changed to X, so please make sure the sequences are sensible proteinsThis is an example (one protein):
>5H2A_CRIGR you can have comments after the ID
MEILCEDNTSLSSIPNSLMQVDGDSGLYRNDFNSRDANSSDASNWTIDGENRTNLSFEGYLPPTCLSILHL
QEKNWSALLTAVVIILTIAGNILVIMAVSLEKKLQNATNYFLMSLAIADMLLGFLVMPVSMLTILYGYRWP
LPSKLCAVWIYLDVLFSTASIMHLCAISLDRYVAIQNPIHHSRFNSRTKAFLKIIAVWTISVGVSMPIPVF
GLQDDSKVFKQGSCLLADDNFVLIGSFVAFFIPLTIMVITYFLTIKSLQKEATLCVSDLSTRAKLASFSFL
PQSSLSSEKLFQRSIHREPGSYTGRRTMQSISNEQKACKVLGIVFFLFVVMWCPFFITNIMAVICKESCNE
HVIGALLNVFVWIGYLSSAVNPLVYTLFNKTYRSAFSRYIQCQYKENRKPLQLILVNTIPALAYKSSQLQA
GQNKDSKEDAEPTDNDCSMVTLGKQQSEETCTDNINTVNEKVSCV
How to run it
Either give the name of the local file in which you have the proteins in the top half of the window, or paste the sequence(s) into the lower part of the window. Then press `Submit'. (It should be possible to both give it a local file and paste sequences if you really want.)Output
There are two output formats: Long and short.Long output format
For the long format (default), tmhmm gives some statistics and a list of the location of the predicted transmembrane helices and the predicted location of the intervening loop regions.Here is an example:
# COX2_BACSU Length: 278
# COX2_BACSU Number of predicted TMHs: 3
# COX2_BACSU Exp number of AAs in TMHs: 68.6888999999999
# COX2_BACSU Exp number, first 60 AAs: 39.8875
# COX2_BACSU Total prob of N-in:
0.99950
# COX2_BACSU POSSIBLE N-term signal sequence
COX2_BACSU TMHMM2.0
inside 1 6
COX2_BACSU TMHMM2.0
TMhelix 7 29
COX2_BACSU TMHMM2.0
outside 30 43
COX2_BACSU TMHMM2.0
TMhelix 44 66
COX2_BACSU TMHMM2.0
inside 67 86
COX2_BACSU TMHMM2.0
TMhelix 87 109
COX2_BACSU TMHMM2.0
outside 110 278
If the whole sequence is labeled as inside or outside, the prediction
is that it contains no membrane
helices. It is probably not wise to interpret it as a prediction
of location. The prediction gives the most probable location and orientation
of transmembrane helices in the sequence. It is found by an algorithm called
N-best (or 1-best in this case) that sums over all paths through the model
with the same location and direction of the helices.
The first few lines gives some statistics:
Length: the length of the protein sequence. Number of predicted TMHs: The number of predicted transmembrane helices. Exp number of AAs in TMHs: The expected number of amino acids intransmembrane helices. If this number is larger than 18 it is very likely to be a transmembrane protein (OR have a signal peptide). Exp number, first 60 AAs: The expected number of amino acids in transmembrane helices in the first 60 amino acids of the protein. If this number more than a few, you should be warned that a predicted transmembrane helix in the N-term could be a signal peptide. Total prob of N-in: The total probability that the N-term is on the cytoplasmic side of the membrane. POSSIBLE N-term signal sequence: a warning that is produced when "Exp number, first 60 AAs" is larger than 10.
Plot of probabilities
The plot shows the posterior probabilities of inside/outside/TM helix. Here one can see possible weak TM helices that were not predicted, and one can get an idea of the certainty of each segment in the prediction.At the top of the plot (between 1 and 1.2) the N-best prediction is shown.
The plot is obtained by calculating the total probability that a residue sits in helix, inside, or outside summed over all possible paths through the model. Sometimes it seems like the plot and the prediction are contradictory, but that is because the plot shows probabilities for each residue, whereas the prediction is the over-all most probable structure. Therefore the plot should be seen as a complementary source of information.
Below the plot there are links to
- The plot in encapsulated postscript
- A script for making the plot in gnuplot.
- The data for the plot.
Short output format
In the short output format one line is produced for each protein with no graphics. Each line starts with the sequence identifier and then these fields:For the example above the short output would be (except that it would be on one line):"len=": the length of the protein sequence. "ExpAA=": The expected number of amino acids intransmembrane helices (see above). "First60=": The expected number of amino acids in transmembrane helices in the first 60 amino acids of the protein (see above). "PredHel=": The number of predicted transmembrane helices by N-best. "Topology=": The topology predicted by N-best.
COX2_BACSU
len=278
ExpAA=68.69
First60=39.89
PredHel=3
Topology=i7-29o44-66i87-109o
The topology is given as the position of the transmembrane helices separated
by 'i' if the loop is on the inside or 'o' if it is on the outside. The
above example 'i7-29o44-66i87-109o' means that it starts on the inside,
has a predicted TMH at position 7 to 29, the outside, then a TMH at position
44-66 etc.
Final remarks
Predicted TM segments in the n-terminal region sometime turn out to be signal peptides.One of the most common mistakes by the program is to reverse the direction of proteins with one TM segment.
Do not use the program to predict whether a non-membrane protein is
cytoplasmic or not.