From Genomes to Proteomes:- Sequence or Structural Relationships Provide Information on Protein Function

One of the important reasons to sequence many genomes is to provide a database that can be used to assign gene functions by genome comparisons, an enterprise referred to as comparative genomics. Sometimes a newly dis covered gene is related by sequence homologies to a gene previously studied in another or the same species, and its function can be entirely or partly defined by that relationship. Such genes—of different species but possessing a clear sequence and functional relationship to each other—are called orthologs. Genes similarly related to each other within a single species are called paralogs (see Fig. 1–37). If the function of a gene has been characterized for one species, this information can be used to assign gene function to the ortholog found in the second species. The identity is easiest to make when comparing genomes from relatively closely related species, such as mouse and human, although many clearly orthologous genes have been identified in species as distant as bacteria and humans. Sometimes even the order of genes on a chromosome is conserved over large segments of the genomes of closely related species (Fig. 9–20). Conserved gene order, called synteny, provides additional evidence for an orthologous relationship between genes at identical locations within the related segments.

Alternatively, certain sequences associated with particular structural motifs (Chapter 4) may be identified within a protein. The presence of a structural motif may suggest that it, say, catalyzes ATP hydrolysis, binds to DNA, or forms a complex with zinc ions, help ing to define molecular function. These relationships are determined with the aid of increasingly sophisticated computer programs, limited only by the current information on gene and protein structure and our capacity to associate sequences with particular structural motifs.

FIGURE 9–20 Synteny in the mouse and human genomes. Large segments of the mouse and human genomes have closely related genes aligned in the same order on chromosomes, a relationship called synteny. This diagram shows segments of human chromosome 9 and mouse chromosome 2. The genes in these segments exhibit a very high degree of homology as well as the same gene order. The different lettering schemes for the gene names reflect different naming conventions in the two organisms.

To further the assignment of function based on structural relationships, a large-scale structural pro teomics project has been initiated. The goal is to crys tallize and determine the structure of as many proteins and protein domains as possible, in many cases with little or no existing information about protein function. The project has been assisted by the automation of some of the tedious steps of protein crystallization. As these structures are revealed. The effort should help define the extent of variation in structural motifs. When a newly discovered protein is found to have structural folds that are clearly related to motifs with known functions in the databases, this information can suggest a molecular function for the protein.

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المجمع العلمي ينظّم سفرة دينية لطلبة مشاريعه القرآنية في كربلاء

عبر مجلّة (تراث الجنوب) المحكّمة.. قسم شؤون المعارف يوثق إرث مدن جنوب العراق

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قسم الشؤون الفكرية وجامعة ميسان يبحثان تعزيز التعاون العلمي المشترك

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مصر تحقق إنجازاً دولياً جديداً في منظمة الصحة العالمية

دراسة: السباحة فعّالة أكثر من الجري في الحفاظ على صحة القلب

عامل خطر في بداية الحمل يؤخر تطور الكلام والمهارات الحركية لدى الرضع

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علماء يكشفون سر سرعة الدلافين في السباحة

سلمي أو دموي.. هكذا تنتقل السلطة في مجتمع الجرذان

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مواضيع ذات صلة

From Genomes to Proteomes:- Detection of Protein-Protein Interactions Helps to Define Cellular and Molecular Function

From Genomes to Proteomes:- Cellular Expression Patterns Can Reveal the Cellular Function of a Gene

From Genes to Genomes:- Genome Sequences Provide the Ultimate Genetic Libraries

From Genes to Genomes:- The Polymerase Chain Reaction Amplifies Specific DNA Sequences

From Genes to Genomes:- DNA Libraries Provide Specialized Catalogs of Genetic Information

DNA Cloning: The Basics:- Alterations in Cloned Genes Produce Modified Proteins

DNA Cloning: The Basics:- Expression of Cloned Genes Produces Large Quantities of Protein

DNA Cloning: The Basics:- Specific DNA Sequences Are Detectable by Hybridization

DNA Cloning: The Basics:- Cloning Vectors Allow Amplification of Inserted DNA Segments

DNA Cloning: The Basics:- Restriction Endonucleases and DNA Ligase Yield Recombinant DNA

Other Functions of Nucleotides:- Adenine Nucleotides Are Components of Many Enzymes Cofactors

Other Functions of Nucleotides:- Nucleotides Carry Chemical Energy in Cells