Targeted mutation of the DNA methyltransferase gene results in embryonic lethality.

We describe a rapid, sensitive process for comprehensively identifying proteins in macromolecular complexes that uses multidimensional liquid chromatography (LC) and tandem mass spectrometry (MS/MS) to separate and fragment peptides. The SEQUEST algorithm, relying upon translated genomic sequences, infers amino acid sequences from the fragment ions. The method was applied to the Saccharomyces cerevisiae ribosome leading to the identification of a novel protein component of the yeast and human 40S subunit. By offering the ability to identify >100 proteins in a single run, this process enables components in even the largest macromolecular complexes to be analyzed comprehensively.

Direct analysis of protein complexes using mass spectrometry

https://www.uab.edu/proteomics/pdf_files/2006/Puig_et_al_Methods.pdf

The tandem affinity purification (TAP) method: a general procedure of protein complex purification.

To identify structural characteristics of the closely related cell surface receptors for insulin and IGF-I that define their distinct physiological roles, we determined the complete primary structure of the human IGF-I receptor from cloned cDNA. The deduced sequence predicts a 1367 amino acid receptor precursor, including a 30-residue signal peptide, which is removed during translocation of the nascent polypeptide chain. The 1337 residue, unmodified proreceptor polypeptide has a predicted Mr of 151,869, which compares with the 180,000 Mr IGF-I receptor precursor. In analogy with the 152,784 Mr insulin receptor precursor, cleavage of the Arg-Lys-Arg-Arg sequence at position 707 of the IGF-I receptor precursor will generate alpha (80,423 Mr) and beta (70,866 Mr) subunits, which compare with approximately 135,000 Mr (alpha) and 90,000 Mr (beta) fully glycosylated subunits.

Insulin-like growth factor I receptor primary structure: comparison with insulin receptor suggests structural determinants that define functional specificity.

Publisher Summary This chapter discusses various methods of estimating protein concentration. Absorption spectroscopy involves the absorption of a photon by an electron. Only those photons with a certain energy level can be absorbed as defined by the difference in energy between the orbital of the unexcited electron and a higher energy orbital. The peptide bond absorbs photons below 210 nm. Because of the large number of peptide bonds in a protein, this is a highly sensitive area of the protein spectrum. Although protein conformation and some absorption by tryptophan and tyrosine residues occurs in this region, less variability between proteins is observed than at 280 nm. There is a need to avoid storing buffers in plastic containers because some plastics leach plasticizers, which absorb at ultraviolet (UV) wavelengths. Detergents can also be troublesome because many absorb UV light. If the buffer or protein solution is cold, the outside of the cuvette may need to be wiped between each reading with a lint-free wiper and the readings should be made quickly after placing the cold solution into the cuvette, because atmospheric moisture may condense on the outside of the cuvette producing an erroneously high reading.

U.I. Flügge

Papers

A method for the quantitative recovery of protein in dilute solution in the presence of detergents and lipids