Stefek Borkowski wrote:
> 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
Well, in that case, I'm not sure. Usually they start counting from the
first amino acid which is '1'... they dont normally start at '0' so that
shouldnt be the problem. I cant help you with that one!
Unless you're not looking at the same protein as they are? Is it exactly
the same? Are there other versions of it that have been sequenced and
placed in the database? Do they give an accession number for the
sequence they're discussing?
Scott.
