Remove 1st character in periodic lines

Hi,
I have a file that looks like this, the unity of information is composed of four lines, and these extends for millions.

My objective is to remove the highligthed "T".

How to attack this? This character is always constant in type "T" and position "1st" but the rest of the line is variable. The positons of the lines are periodics of every 2nd, 6st, 10th... lines, and upstream and downstream lines always start with "@" and "+". The fourth line might contain a "T" in the 1st position which I don't want to remove

Iknow the basics of unix commands.

Cheers!

$ sed 's,^T,,g' infile

Perfect!
's,^T,,g' ---> Going to look who is who and doing what...

cheers!

sed will remove the alphabet T if it is the first character in a file ..

Sed basics .. http://sed.sourceforge.net/sed1line.txt

But it will remove if is 1st character in every line? I might have "T" in 4th, 8th, 12th,... that I don't want to remove. Either way if that's the case, further upstream I will have a error warning.

So what is your expected output based on your input file ..

You can supply an address (e.g. a line number) in sed commands to restrict the lines it changes.

For example, sed '2 s,^T,,g' would only operate on line 2, sed '2~4 s,^T,,g ' is line 2 and every 4th line after that.

Is exactly that, to be specific in which line it replace, in my case from the 2nd and then every 4th plus line.
Thank you both!