Scott Coutts wrote:
> Stefek Borkowski wrote:
>> Hi,
>> Can someone explain how the length of protein sequence, i.e. the
>> number of amino acid residues, should be properly counted. I try to
>> assess the length of human heart fatty acid binding protein. It is
>> physically built of 133 amino acids, but for some reason the
>> literature value is 132. It seems like the paper purposely omits the
>> first methionine. Also the numbering of amino acids goes this way,
>> as if the starting methionine is not present. Would you please
>> comment on this. Thank you in advance. Regards,
>> Stefek
>> Sometimes the first amino acid is removed proteolytically after the
> protein is produced.
Hi again Scott. I have just expressed my thanks to you in the below thread
:) Thanks again!
As for your answer above I must admit I am a bit confused. All I know is
that the FABPs (Fatty Acid Binding Proteins) are cytosolic ones, they
possess no signal sequence to be cleaved. The first methionine is always
acetylated, it is present in the crystallographic structure analyses and
all, so I do believe it physically exists and must not be omitted. Below I
give you the complete sequence of human heart fatty acid binding protein
(H-FABP). To me the only cysteine is at the position 125, and the paper
claims it is 124. The similar numbering is used for other FABPs, so I do not
consider it an accidental typo. How should I interprete this, and finally
how should I refer to that cysteine in H-FABP, namely 124 or 125?! Could you
elaborate a bit on that statement of yours concerning the removal of the
first amino acid from a synthesized protein? Is this a common phenomenon?! I
have never heard of this...
Thanks so much in advance.
Stefek
