Ter: number of amino acids

[Anna Matys]

Dear HGVS team,

how many amino acids does the protein with the mutation p.(Gln1756ProfsTer74) contain?

Is it 1756 + 74 (so 1830) or 1756 + 73 (so 1829) because the last position is termination and there is no specific amino acid that would terminate the synthesis?

Best regards,

Anna

[Johan den Dunnen]

Dear Anna,

p.(Gln1756ProfsTer74) means the predicted consequences of a variant (which you do not give but is mandatory to report) contains a Ter codon at position 74 of the shifted reading frame. The protein therefor is translated into 1756 + 73 = 1829 amino acids. Modification of the mature protein may remove additional amino acids, starting with the Met at position1.

Best regards,

Johan den Dunnen
HUGO HGVS Variant Nomenclature Committee (HVNC)

Op dinsdag 23 juni 2026 om 13:21:13 UTC+2 schreef Anna Matys:

[Scott McMahan]

My reading of the rule is that the initial translation produces an 1828 amino acid protein since 1756 is the first position of the first new amino acid. So we have 1755 amino acids that match reference sequence + 73 shifted frame amino acids + termination at fs position 74. If that is incorrect, then the notes at Frameshift - HGVS Nomenclature should clarify further.

 

From: hgvs-nom...@googlegroups.com <hgvs-nom...@googlegroups.com> On Behalf Of Johan den Dunnen
Sent: Thursday, June 25, 2026 7:46 AM
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Subject: [hgvs-nomenclature] Re: Ter: number of amino acids

 

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[Raymond Dalgleish]

I am intrigued by your question " how many amino acids does the protein with the mutation p.(Gln1756ProfsTer74) contain?"

A premature termination codon will, in most cases, trigger nonsense mediate decay (NMD) of the variant transcript resulting in no protein being produced at all.