CHAPTER 24 – Evolution of Protein Molecules

Proteins from silver-stained gels can be digested enzymatically and the resulting peptides analyzed and sequenced by mass spectrometry. Standard proteins yield the same peptide maps when extracted from Coomassie- and silver-stained gels, as judged by electrospray and MALDI mass spectrometry. The low nanogram range can be reached by the protocols described here, and the method is robust. A silver-stained one-dimensional gel of a fraction from yeast proteins was analyzed by nanoelectrospray tandem mass spectrometry. In the sequencing, more than 1000 amino acids were covered, resulting in no evidence of chemical modifications due to the silver staining procedure. Silver staining allows a substantial shortening of sample preparation time and may, therefore, be preferable over Coomassie staining. This work removes a major obstacle to the low-level sequence analysis of proteins separated on polyacrylamide gels.

Mass Spectrometric Sequencing of Proteins from Silver-Stained Polyacrylamide Gels

Traffic signals for lymphocyte recirculation and leukocyte emigration: The multistep paradigm

Integrins: a family of cell surface receptors.

The integration and control of systemic immune responses depends on the regulated trafficking of lymphocytes. This lymphocyte "homing" process disperses the immunologic repertoire, directs lymphocyte subsets to the specialized microenvironments that control their differentiation and regulate their survival, and targets immune effector cells to sites of antigenic or microbial invasion. Recent advances reveal that the exquisite specificity of lymphocyte homing is determined by combinatorial "decision processes" involving multistep sequential engagement of adhesion and signaling receptors. These homing-related interactions are seamlessly integrated into the overall interaction of the lymphocyte with its environment and participate directly in the control of lymphocyte function, life-span, and population dynamics. In this article a review of the molecular basis of lymphocyte homing is presented, and mechanisms by which homing physiology regulated the homeostasis of immunologic resources are proposed.

https://science.sciencemag.org/content/sci/272/5258/60.full.pdf

Lymphocyte homing and homeostasis.

Rhodopsin content in the outer segment membranes of bovine and frog retinal rods.

The use of retrograde axonal transport of various substances (for example, enzymes, lectins, synthetic fluorescent compounds) has yielded much information on the organization of neuronal pathways. Each type of retrograde tracer has its own set of attributes which define the scope of problems it can address. We describe here a new class of retrograde tracer, rhodamine-labelled fluorescent latex microspheres (0.02-0.2 micron diameter), which have distinct advantages over other available tracers for in vivo and in vitro applications. When injected into brain tissue, these microspheres show little diffusion and consequently produce small, sharply defined injection sites. Once transported back to neuronal somata, the label persists for at least 10 weeks in vivo and 1 yr after fixation. Microspheres have no obvious cytotoxicity or phototoxicity as assessed by intracellular recording and staining of retrogradely labelled cells in a cortical brain slice preparation. This approach was further used to visualize and compare, in cat visual cortex slices, neurones with different projection patterns, and revealed significant differences in patterns of intrinsic axons and dendrites. These properties of microspheres open new avenues for anatomical and physiological studies of identified projection neurones in slices as well as in dissociated cell cultures.

Fluorescent latex microspheres as a retrograde neuronal marker for in vivo and in vitro studies of visual cortex

https://febs.onlinelibrary.wiley.com/doi/pdf/10.1016/0014-5793%2872%2980002-4

Light dependent phosphorylation of rhodopsin by ATP.

p97 is a 97,000-molecular weight (MW) cell-surface glyco-protein, which is present in most human melanomas but in only trace amounts in normal tissues1–4. We describe here the purification of p97 by affinity chromatography with monoclonal antibody, followed by SDS-polyacrylamide gel electrophoresis (SDS-PAGE), and determination of the N-terminal amino acid sequence using a new, highly sensitive protein sequencer5. The sequence was found to be homologous to the N-terminal sequences of transferrin and lactotransferrin. This structural homology was confirmed by the observation that antiserum to denatured p97 cross-reacted with denatured transferrin and lactotransferrin. We have also demonstrated that p97 is functionally related to transferrin and lactotransferrin in that it binds iron. This is one of the first reports of the amino acid sequence of a human tumour-associated cell-surface antigen and one of the few cases in which insight has been obtained into its function.

William J. Dreyer

Papers

Rhodopsin content in the outer segment membranes of bovine and frog retinal rods.

Fluorescent latex microspheres as a retrograde neuronal marker for in vivo and in vitro studies of visual cortex

Light dependent phosphorylation of rhodopsin by ATP.

Human melanoma-associated antigen p97 is structurally and functionally related to transferrin

Light Chain Evolution