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IMGT reference sequences in FASTA format:

Amino acid sequences with gaps

The FASTA header contains:
IMGT accession number | gene and allele name | species | functionality | exon name | domain name | domain type | alternative splicing (if it is) | partial (if it is) 
>AL672024|CD28*01|Mus musculus|F|EX1|
MTLRLLFLALNFFSVQVT
>AL672024|CD28*01|Mus musculus|F|EX2|[D]|V-LIKE|
ENKILVKQSPLLVVDSNEVSLSCRYSYNLLA...KEFRASLYKGV.NSDVEVCVGNGNFT
.YQPQFRSNAE....FNCDGDFDNETVTFRLWNLHVNHTDIYFCKIEFMYPPPYLDNERS
NGTIIHIK
>AL672024|CD28*01|Mus musculus|F|EX3|
EKHLCHTQSSPKLFWALVVVAGVLFCYGLLVTVALCVIW
>AL672024|CD28*01|Mus musculus|F|EX4|
TNSRRNRLLQSDYMNMTPRRPGLTRKPYQPYAPARDFAAYRP