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Prokaryotic Initiation Factors: Peptide initiation factors from prokaryotic organisms. Only three factors are needed for translation initiation in prokaryotic organisms, which occurs by a far simpler process than in PEPTIDE CHAIN INITIATION, TRANSLATIONAL of eukaryotic organisms.Prokaryotic Initiation Factor-1: The smallest of the three prokaryotic initiation factors with a molecular size of approximately 8 kD. It binds near the A-site of the 30S subunit of RIBOSOMES and may play a role in preventing premature addition of aminoacyl-tRNA-linked PEPTIDE ELONGATION FACTOR TU to the ribosome during the initiation of a peptide chain (PEPTIDE CHAIN INITIATION, TRANSLATIONAL).Peptide Initiation Factors: Protein factors uniquely required during the initiation phase of protein synthesis in GENETIC TRANSLATION.Prokaryotic Initiation Factor-3: A prokaryotic initiation factor that plays a role in recycling of ribosomal subunits for a new round of translational initiation. It binds to 16S RIBOSOMAL RNA and stimulates the dissociation of vacant 70S ribosomes. It may also be involved in the preferential binding of initiator tRNA to the 30S initiation complex.Prokaryotic Initiation Factor-2: The largest of the three prokaryotic initiation factors with a molecular size of approximately 80 kD. It functions in the transcription initiation process by promoting the binding of formylmethionine-tRNA to the P-site of the 30S ribosome and by preventing the incorrect binding of elongator tRNA to the translation initiation site.Prokaryotic Cells: Cells lacking a nuclear membrane so that the nuclear material is either scattered in the cytoplasm or collected in a nucleoid region.Eukaryotic Initiation Factors: Peptide initiation factors from eukaryotic organisms. Over twelve factors are involved in PEPTIDE CHAIN INITIATION, TRANSLATIONAL in eukaryotic cells. Many of these factors play a role in controlling the rate of MRNA TRANSLATION.Eukaryotic Initiation Factor-2: Eukaryotic initiation factor of protein synthesis. In higher eukaryotes the factor consists of three subunits: alpha, beta, and gamma. As initiation proceeds, eIF-2 forms a ternary complex with Met-tRNAi and GTP.Eukaryotic Initiation Factor-4E: A peptide initiation factor that binds specifically to the 5' MRNA CAP STRUCTURE of MRNA in the CYTOPLASM. It is a component of the trimeric complex EIF4F.Eukaryotic Initiation Factor-3: A multisubunit eukaryotic initiation factor that contains at least 8 distinct polypeptides. It plays a role in recycling of ribosomal subunits to the site of transcription initiation by promoting the dissociation of non-translating ribosomal subunits. It also is involved in promoting the binding of a ternary complex of EUKARYOTIC INITIATION FACTOR-2; GTP; and INITIATOR TRNA to the 40S ribosomal subunit.Peptide Chain Initiation, Translational: A process of GENETIC TRANSLATION whereby the formation of a peptide chain is started. It includes assembly of the RIBOSOME components, the MESSENGER RNA coding for the polypeptide to be made, INITIATOR TRNA, and PEPTIDE INITIATION FACTORS; and placement of the first amino acid in the peptide chain. The details and components of this process are unique for prokaryotic protein biosynthesis and eukaryotic protein biosynthesis.Eukaryotic Initiation Factor-4G: A component of eukaryotic initiation factor-4F that is involved in multiple protein interactions at the site of translation initiation. Thus it may serve a role in bringing together various initiation factors at the site of translation initiation.Protein Biosynthesis: The biosynthesis of PEPTIDES and PROTEINS on RIBOSOMES, directed by MESSENGER RNA, via TRANSFER RNA that is charged with standard proteinogenic AMINO ACIDS.Eukaryotic Initiation Factor-4A: A component of eukaryotic initiation factor 4F that as an RNA helicase involved in unwinding the secondary structure of the 5' UNTRANSLATED REGION of MRNA. The unwinding facilitates the binding of the 40S ribosomal subunit.Eukaryotic Initiation Factor-4F: A trimeric peptide initiation factor complex that associates with the 5' MRNA cap structure of RNA (RNA CAPS) and plays an essential role in MRNA TRANSLATION. It is composed of EUKARYOTIC INITIATION FACTOR-4A; EUKARYOTIC INITIATION FACTOR-4E; and EUKARYOTIC INITIATION FACTOR-4G.Ribosomes: Multicomponent ribonucleoprotein structures found in the CYTOPLASM of all cells, and in MITOCHONDRIA, and PLASTIDS. They function in PROTEIN BIOSYNTHESIS via GENETIC TRANSLATION.Eukaryotic Initiation Factor-1: A eukaryotic initiation factor that binds to 40S ribosomal subunits. Although initially considered a "non-essential" factor for eukaryotic transcription initiation, eukaryotic initiation factor-1 is now thought to play an important role in localizing RIBOSOMES at the initiation codon of MRNA.Molecular Sequence Data: Descriptions of specific amino acid, carbohydrate, or nucleotide sequences which have appeared in the published literature and/or are deposited in and maintained by databanks such as GENBANK, European Molecular Biology Laboratory (EMBL), National Biomedical Research Foundation (NBRF), or other sequence repositories.Eukaryotic Initiation Factor-2B: A guanine nucleotide exchange factor that acts to restore EUKARYOTIC INITIATION FACTOR-2 to its GTP bound form.RNA, Transfer, Met: A transfer RNA which is specific for carrying methionine to sites on the ribosomes. During initiation of protein synthesis, tRNA(f)Met in prokaryotic cells and tRNA(i)Met in eukaryotic cells binds to the start codon (CODON, INITIATOR).Reticulocytes: Immature ERYTHROCYTES. In humans, these are ERYTHROID CELLS that have just undergone extrusion of their CELL NUCLEUS. They still contain some organelles that gradually decrease in number as the cells mature. RIBOSOMES are last to disappear. Certain staining techniques cause components of the ribosomes to precipitate into characteristic "reticulum" (not the same as the ENDOPLASMIC RETICULUM), hence the name reticulocytes.