https://science.sciencemag.org/content/sci/197/4299/127.full.pdf

The vertebrate eye lens.

Chapter 3 – The Lens: Development, Proteins, Metabolism and Cataract

Publisher Summary This chapter discusses the deamidation of glutaminyl and asparaginyl residues in peptides and proteins. The occurrence of glutaminyl and asparaginyl residues in peptides and proteins is so widespread that these residues have become known as 2 of the 20 most commonly occurring amino acid residues. It has been hypothesized that these residues play static roles in protein structure and also play dynamic roles as molecular timers of biological events. Deamidation of glutaminyl and asparaginyl residues has been responsible for artifacts in peptide and protein chemistry. The rate of deamidation of these residues has been shown to be dependent upon primary sequence, secondary and tertiary structure, temperature, pH, ionic strength, and special intermolecular interactions. Deamidation has been found to occur in a wide variety of different proteins and may be expected to occur in most proteins under physiological conditions. Many of the essential processes in living things may be timed by deamidation of glutaminyl and asparaginyl residues. These molecular timers are under simple genetic control, are adjustable to many different timed intervals, and are easily implementable by means of the important changes that they can effect in the proteins in which they are included.

Deamidation of Glutaminyl and Asparaginyl Residues in Peptides and Proteins

The vertebrate lens comprises cells from only one cell lineage and these exist in two distinct forms Fibre cells make up the bulk of the lens and a monolayer of epithelial cells covers the anterior surface of the fibres A quantitative analysis of cell division and cell specialization (elongation) in the lenses of 1-day-old and 6- to 7-week-old rats showed that the rat lens can be separated into two compartments; a proliferation compartment in the epithelium of the anterior lens and an elongation compartment in the posterior lens In 6- to 7-week-old rats the proliferation compartment is divided into three sub-compartments which appear to be related to the anatomy of the anterior eye Lens epithelial cells lying in the vicinity of the ciliary body have an average cell cycle time of 7·2 days, epithelial cells which lie below the iris have an average cell cycle time of 32·3 days, and cells in the central epithelium divide most slowly The epithelium is bathed for the most part by the aqueous humour and the posterior part of the lens is surrounded by the vitreous humour From this analysis as well as evidence from other laboratories it is suggested that a proliferation factor(s) may be present in the aqueous and that an elongation factor(s) which comes from the retina may be present in the vitreous There are three major groups of lens specific proteins, α-, β- and γ-crystallins These proteins were separated by gel chromatography and antibodies raised against them in rabbits Alpha-, β- and γ-crystallins were localized in sections of the 1-day-old rat lens by the indirect immunofluorescence method Epithelial cells in the proliferation compartment contained only α-crystallin but all three groups of crystallins were detected in cells of the elongation compartment β-Crystallin was detected first in elongating cells that had stopped dividing and γ-crystallin was detected later in the elongation process Thus, synthesis of β- and γ-crystallins may normally depend on the elongation factor(s) from the retina Also, since there is a close relationship between cessation of cell division and detection of β-crystallin, another factor governing the synthesis of β-crystallin may be whether the cells have ceased dividing In this way the expression of crystallin genes may be co-ordinated as the lens grows and cells make the transition from proliferation to elongation compartments

Cell division, cell elongation and distribution of α-, β- and γ-crystallins in the rat lens

Laser Raman spectroscopic studies of ocular lens and its isolated protein fractions.

Characteristics of α-crystallin related to fiber cell development in calf eye lenses

The development of the eye lens in the prenatal phase is accompanied by a gradual change in the polypeptide composition of α-crystallin. As the lens matures from that of a 6-week-old embryo to that of a new-born calf, there is a successive appearance of different polypeptides although two obviously principal polypeptides, A2 and B2, are present at every stage of development. The youngest embryonic lenses studied contain four polypeptides. Two of them differ from the well-known polypeptides as found in cortical bovine α-crystallin.

Specific polypeptides in prenatal bovine alpha-crystallin.

Reaggregation studies on the polypeptide chains of calf lens α-crystallin

Heterogeneity, aging and polypeptide composition of α-crystallin from calf lens

1. 1. Lenses of bovine embryos and fetuses, ranging in age from 6 weeks to 9 months, were investigated. 2. 2. Weight, shape, protein content and protein composition as well as leucine aminopeptidase activity were determined as a function of age. 3. 3. Alpha-crystallin turned out to be the most prominent embryonic crystallin. 4. 4. The complexity of the protein composition of the lens increased in maturity up to birth. 5. 5. The polypeptide composition of the α-crystallins was analyzed by means of isoelectric focusing in polyacrylamide gels. Two polypeptides, specifiic for the embryonic lenses, were found. 6. 6. One of these specific polypeptides appeared to be sensitive to u.v. light.

The soluble proteins of the prenatal bovine eye lens.

Popular Tasks used by Researchers

How can I help with your research?

Get more enhanced response by uploading the PDFs you want me to reference.

No relevant PDFs in your library

SciSpace is the AI research assistant for academics. Run systematic literature reviews on 280M+ papers, and write papers with cited sources. Trusted by 1M+ students, PhDs & researchers.

SciSpace | AI for Research

We encountered an error while loading the panel. Please try refreshing the page.

Something went wrong

Analyze PDFs

Code & Manuscripts

Funding & Grants

Literature & Patents

Medical & Clinical Data

Systematic Review

Visualize & Present

Web & Data

Build a Google Scholar-like website for your research.

Build a website

Create charts and images for your research

Create a Chart

Write a paper for submission to a journal

Draft a manuscript

Patent Search

Design eye-catching scientific posters in minutes.

Scientific Poster Generation

Systematic Literature Review

Anyone with the link can view this chat. You can switch it back to private anytime.

One task is running at the moment. Your messages will be shown right after.

Drag and drop or click here to browse

Loved by <highlight>1 million+</highlight> researchers

Extract a list of specific topics and their sources from unstructured text

Topics

Compare and analyze relevant papers that matches with your search

Papers

Get insights from PDFs and bookmarked papers from your library

My library

Recent searches

Try searching for:

Catch AI-generated content in scholarly and non-scholarly content

{ai} Detector

Ai Writer

Get PDF Summaries, highlighted text explanations 

Chat with PDF

Effortlessly create in-text citations and bibliographies in APA and 2,500 other formats

Citation generator

Get explanations, summaries, and answers on academic papers

Ease up your research workflow with {scispace}'s cohort of exciting AI tools

Elevate your academic writing skills and convey your ideas the way you want

Paraphraser

Explore our range of reading and writing tools

Your file is being prepared and should be ready in a few minutes. If it's a large file, it might take a bit longer. You can close this window, and we'll email you the file when it's done.

You have reached a maximum limit of <strong>{limit}</strong> columns in the table. Remove at least <strong>1</strong> column to add or create another one.

Gerard J. van Kamp

Author Tools

Chat about Author