PTM_small

A post-translational modification prediction model based on [ESM2-8M model] (https://www.science.org/doi/full/10.1126/science.ade2574) fine-tuning.

The dataset comes from the [PTM-Mamba project] (https://github.com/programmablebio/ptm-mamba?tab=readme-ov-file).

Modifications of the same type for different amino acids are merged, and rare modifications are merged into the same class.

from transformers import AutoModelForTokenClassification, AutoTokenizer
import torch

model_id = "leexiaohua/PTM_small"

tokenizer = AutoTokenizer.from_pretrained(model_id)
model = AutoModelForTokenClassification.from_pretrained(model_id)

device = torch.device("cuda" if torch.cuda.is_available() else "cpu")
model.to(device)
model.eval()

def probe_ptm(sequence, threshold=0.5):

    # 1. Tokenize and move to device
    inputs = tokenizer(sequence, return_tensors="pt", truncation=True, max_length=1024)
    tokens = tokenizer.convert_ids_to_tokens(inputs["input_ids"][0])
    inputs = {k: v.to(device) for k, v in inputs.items()}
    
    # 2. Model Inference
    with torch.no_grad():
        logits = model(**inputs).logits
        probs = torch.softmax(logits, dim=-1)

    # 3. Class Mapping
    ptm_map = {
        1: "Phospho", 
        2: "Acetyl", 
        3: "Methyl", 
        4: "Glycosyl", 
        5: "Lipid", 
        6: "Rare"}
    
    print(f"--- Scanning sequence with {threshold:.0%} sensitivity (Bidirectional Alignment) ---")
    
    seq_idx = 0 
    found = False

    for i, token in enumerate(tokens):
        # Skip special tokens like <cls>, <sep>, <pad>
        if token.startswith("<") or token.endswith(">"):
            continue
            
        # Extract probabilities for the current residue
        res_probs = probs[0][i]
        mod_probs = res_probs[1:]  # Exclude 'None' class (index 0)
        max_mod_prob, max_mod_idx = torch.max(mod_probs, dim=0)
        actual_label_idx = max_mod_idx.item() + 1
        
        if max_mod_prob > threshold:
            amino_acid = sequence[seq_idx]
            actual_position = seq_idx + 1  
         
            # Verify token alignment with original sequence
            if token.upper() != amino_acid.upper():
                # Potential alignment warning can be added here if needed
                pass

            print(f"Position {actual_position}: {amino_acid} -> Likely {ptm_map[actual_label_idx]} (Confidence: {max_mod_prob:.2%})")
            found = True
            
        seq_idx += 1 

    if not found:
        print("No PTM sites found above the specified threshold.")

test_seq = "MLPGLALLLLAAWTARALEVPTDGNAGLLAEPQIAMFCGRLNMHMNVQNGKWDSDPSGTKTCIDTKEGILQYCQEVYPELQITNVVEANQPVTIQNWCKRGRKQCKTHPHFVIPYRCLVGEFVSDALLVPDKCKFLHQERMDVCETHLHWHTVAKETCSEKSTNLHDYGMLLPCGIDKFRGVEFVCCPLAEESDNVDSADAEEDDSDVWWGGADTDYADGSEDKVVEVAEEEEVAEVEEEEADDDEDDEDGDEVEEEAEEPYEEATERTTSIATTTTTTTESVEEVVREVCSEQAETGPCRAMISRWYFDVTEGKCAPFFYGGCGGNRNNFDTEEYCMAVCGSAMSQSLLKTTQEPLARDPVKLPTTAASTPDAVDKYLETPGDENEHAHFQKAKERLEAKHRERMSQVMREWEEAERQAKNLPKADKKAVIQHFQEKVESLEQEAANERQQLVETHMARVEAMLNDRRRLALENYITALQAVPPRPRHVFNMLKKYVRAEQKDRQHTLKHFEHVRMVDPKKAAQIRSQVMTHLRVIYERMNQSLSLLYNVPAVAEEIQDEVDELLQKEQNYSDDVLANMISEPRISYGNDALMPSLTETKTTVELLPVNGEFSLDDLQPWHSFGADSVPANTENEVEPVDARPAADRGLTTRPGSGLTNIKTEEISEVKMDAEFRHDSGYEVHHQKLVFFAEDVGSNKGAIIGLMVGGVVIATVIVITLVMLKKKQYTSIHHGVVEVDAAVTPEERHLSKMQQNGYENPTYKFFEQMQN"
probe_ptm(test_seq, threshold=0.2)

The output will be similar to:

--- Scanning sequence with 20% sensitivity (Bidirectional Alignment) ---
Position 198: S -> Likely Phospho (Confidence: 74.38%)
Position 206: S -> Likely Phospho (Confidence: 79.13%)
Position 217: Y -> Likely Rare (Confidence: 90.77%)
Position 262: Y -> Likely Rare (Confidence: 59.31%)
Position 336: Y -> Likely Rare (Confidence: 67.14%)
Position 441: S -> Likely Phospho (Confidence: 79.16%)
Position 497: Y -> Likely Phospho (Confidence: 44.33%)
Position 542: N -> Likely Glycosyl (Confidence: 95.32%)
Position 571: N -> Likely Glycosyl (Confidence: 88.64%)
Position 729: T -> Likely Phospho (Confidence: 79.49%)
Position 730: S -> Likely Phospho (Confidence: 95.94%)
Position 757: Y -> Likely Phospho (Confidence: 48.01%)