BLAST

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Chapter 2: Biological Sequences

Using one-letter symbols, a protein sequence might be written like this:

MLVGSRA

Like DNA and RNA, proteins also have polarity, and the nomenclature comes from

the chemical structure. Here again, the convention is to display the sequence from

left to right. In proteins, the left end is called the N-terminus and the right end is

called the C-terminus. Thus, when people say, “the N-terminus is often removed

Asparagine Asn N Neutral ;

hydrophilic

Proline Pro P Hydrophobic

Glutamine Gln Q Neutral ;

hydrophilic

Arginine Arg R Positively charged

Serine Ser S Neutral;

hydrophilic

Threonine Thr T Neutral ;

hydrophilic

Valine Val V Hydrophobic

Tryptophan Trp W Hydrophobic;

aromatic

Tyrosine Tyr Y Hydrophobic;

aromatic

Table 2-2. Amino acids (continued)

Amino acid Abbreviation Symbol Properties Structure

OH

NH

2

O

O

H

2

N

OH

O

NH

OH

NH

2

O

H

2

N

O

OH

NH

2

O

H

2

N

NH

N

H

OH

NH

2

O

HO

OH

NH

2

OOH

OH

NH

2

O

OH

O

N

H

NH

2

OH

O

NH

2

HO

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The Central Dogma of Molecular Biology

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after translation,” they’re talking about the beginning of the protein. Remember that

all proteins start with the amino acid methionine (M).