Protein motif /domain Structural unit Functional unit Signature of protein family How are they defined?

How do we represent the position specific preference ? BID_MOUSE I A R H L A Q I G D E M BAD_MOUSE Y G R E L R R M S D E F BAK_MOUSE V G R Q L A L I G D D I BAXB_HUMAN L S E C L K R I G D E L BimS I A Q E L R R I G D E F HRK_HUMAN T A A R L K A L G D E L Egl-1 I G S K L A A M C D D F Binary pattern: L [GSC] [HEQCRK] X [^ILMFV] Basic concept of motif identification 2.

How do we represent the position specific preference ? BID_MOUSE I A R H L A Q I G D E M BAD_MOUSE Y G R E L R R M S D E F BAK_MOUSE V G R Q L A L I G D D I BAXB_HUMAN L S E C L K R I G D E L BimS I A Q E L R R I G D E F HRK_HUMAN T A A R L K A L G D E L Egl-1 I G S K L A A M C D D F Statistical representation G: 5 -> 71% S: 1 -> 14 % C: 1 -> 14 % Basic concept of motif identification 2.

Scoring sequence based on Model Seq: A S L D E L G D E A C D ….... position_1 = s(A/1) + s(S/2) + s(L/3) + s(D / 4) An example of position specific matrixexample

Representation of positional information in specific motif M-C-N-S-S-C-[MV]-G-G-M-N-R-R. Binary patterns: Positional matrix:

Hidden Markov Model A specification on “how events will happen” so that statistical assessment can be readily made Used for Speech recognition and characterizing sequence patterns

Hidden Markov Model Position 1Position 2 Deletion Insertion Position 3 1.) possible states of events or “routes” --Transition Probability

Hidden Markov Model Position 1Position 2 2.) possible AA at a given position -- emission probability ACDEFGHIACDEFGHI

Hidden Markov Model 3.) That’s all. Let’s give it a try and you will know what it is about

Hidden Markov Model How to make a HMM for my petty motif Collect related sequences MEME : bin/meme.cgi *Selection of sequences determines the model*

Identifying motifs using MEME -Multiple EM for Motif Elicitation EM: Expectation maximization (P ). Identifies statistically significant motif(s) in a set of sequences. Outline the occurrence of the motifs at the end of the report

Practice: Identify conserved motifs using MEME 1.) Input your own address. 2.) Load the file of multiple Fasta format sequences. 3.) You can change other options based on your needs.

Two search examples  The outcome of the search is dependent on the inputting set of sequences.  Compose the inputting set based on your research needs. Set1: Mammalian P53 plus mosquito hits Set2: Diverse set of P53 plus mosquito hits

Two search examples Set1: Mammalian P53 plus mosquito hits Set2: Diverse set of P53 plus mosquito hits

Secondary structure prediction Predict the likelihood of amino acid x to be in each of the three (four) types of secondary structure configuration Helix Sheet Turn Coil Coiled-coil is two helices tangled together

Secondary structure prediction - different strategies and algorithms Chou-Fasman / Garnier Method -- based on AA composition Nearest Neighbor / Levin Method -- based on sequence similarity Neural Network / PHD SOPM, DPM, DSC, etc.

Results are given at single amino acid level

Secondary structure prediction --Interpretation of result Seq: - D G S L A D E R K Pre: - B B B H H B B T T What is the likelihood of helix formation here ?

Secondary structure prediction -Accuracy At the amino acid level -- ~ 75% based on testing set IF: Seq: - D G I L A V A S M I V Pre: - B B H H H H H H H H H Length > 9 > 90% chance a helix formation around this region

Secondary structure prediction -Programs There are over a dozen web sites provide 2 nd structure predication service – (tools) AntheWin has a good sample of different approaches and has other associated tools

Practice: using AnathePro to analyze protein secondary structure Open the sequence file. Chose and run a secondary structure predication method from the “Methods” menu LEFT click the left boundary of an alpha helix and then RIGHT the right boundary, perform “helical Wheel”

Helix wheel to discern helix subtype HydrophilicHydrophobicOthers AmphipathicHydrophobicHydrophilic