use strict;
use warnings;
use Data::Dumper;

local $/=">";
while(my $fasta_record=<DATA>){
	chomp $fasta_record;
	$fasta_record =~ s/(^>*.+\n)/$1: /;  #add a space after the fasta header 
	$fasta_record =~ s/\n//g;  # remove endlines
	print $fasta_record,"\n";
	}

__DATA__
>protein1
WWWWTCTG
TTWTTTCT
TTWWWC
>protein2
WWWWTCTG
TTWWWC
TTWTTTCT
>protein3
TTWWWC
WWWWTCTG
TTWTTTCT