Proteins are polymers composed of hundreds or even thousands of amino acids linked in series by peptide bonds. What structural forms do these polypeptide chains assume, how can the sequence of amino acids in a protein be determined, and what are the biological roles played by proteins? | CHAPTER 5 Proteins: Their Biological Functions and Primary Structure to accompany Biochemistry, 2/e by Reginald Garrett and Charles Grisham All rights reserved. Requests for permission to make copies of any part of the work should be mailed to: Permissions Department, Harcourt Brace & Company, 6277 Sea Harbor Drive, Orlando, Florida 32887-6777 Outline Proteins - Linear Polymers of Amino Acids Architecture Many Biological Functions May be Conjugated with Other Groups Primary Structure Determination Consider the Nature of Sequences Proteins are Linear Polymers of Amino Acids The Peptide Bond is usually found in the trans conformation has partial (40%) double bond character is about nm long - shorter than a typical single bond but longer than a double bond Due to the double bond character, the six atoms of the peptide bond group are always planar! N partially positive; O partially negative The Coplanar Nature of the Peptide Bond Six atoms of the peptide group lie in a plane! “Peptides” Short polymers of amino acids Each unit is called a residue 2 residues - dipeptide 3 residues - tripeptide 12-20 residues - oligopeptide many - polypeptide “Protein” One or more polypeptide chains One polypeptide chain - a monomeric protein More than one - multimeric protein Homomultimer - one kind of chain Heteromultimer - two or more different chains Hemoglobin, for example, is a heterotetramer It has two alpha chains and two beta chains Proteins - Large and Small Insulin - A chain of 21 residues, B chain of 30 residues -total mol. wt. of 5,733 Glutamine synthetase - 12 subunits of 468 residues each - total mol. wt. of 600,000 Connectin proteins - alpha - MW million! beta connectin - MW of million, with a length of 1000 nm -it can stretch to 3000 nm! The Sequence of Amino Acids in a Protein is a unique characteristic of every protein is encoded by the nucleotide sequence of DNA is thus a form of genetic information is read from the amino . | CHAPTER 5 Proteins: Their Biological Functions and Primary Structure to accompany Biochemistry, 2/e by Reginald Garrett and Charles Grisham All rights reserved. Requests for permission to make copies of any part of the work should be mailed to: Permissions Department, Harcourt Brace & Company, 6277 Sea Harbor Drive, Orlando, Florida 32887-6777 Outline Proteins - Linear Polymers of Amino Acids Architecture Many Biological Functions May be Conjugated with Other Groups Primary Structure Determination Consider the Nature of Sequences Proteins are Linear Polymers of Amino Acids The Peptide Bond is usually found in the trans conformation has partial (40%) double bond character is about nm long - shorter than a typical single bond but longer than a double bond Due to the double bond character, the six atoms of the peptide bond group are always planar! N partially positive; O partially negative The Coplanar Nature of the Peptide Bond Six atoms of the peptide
