# Bacterial Microcompartment Cargo Packing and Ultrastructure: High-Resolution Studies of Native Alpha-Carboxysomes

> **NIH NIH F32** · CALIFORNIA INSTITUTE OF TECHNOLOGY · 2020 · $67,446

## Abstract

Project Summary/Abstract
Bacteria lack organelles, yet some enzymatic pathways generate intermediates which are either susceptible to
loss or which could be toxic to the cell if released into the cytosol. Roughly 20% of bacteria encase the potentially
dangerous or inefficient components of these pathways inside bacterial microcompartments (BMCs). BMCs have
been characterized in a number of species, and serve a variety of roles from carbon fixation to small molecule
metabolism. They typically contain two or more enzymes, a variable number of accessory and scaffolding
proteins, and a compact protein shell that is selectively permeable to small molecules without the aid of a lipid
membrane. The shell proteins and the heterogeneous composition of the shell are conserved across all BMCs
of all functions characterized thus far. Because BMCs can allow bacteria to live in hostile environments, they
have broad implications for human health, ecology and infectious disease. BMCs have also become a target of
protein engineering due to their potential for enclosing cargos of choice for alternative pharmacological and
biotechnological applications, as well as for their basic value as a critical component of many species’
metabolism. Despite their importance, structural heterogeneity has prevented a complete understanding of
architecture, ultrastructure, and spatial organization of both the shell proteins and the cargo. The research
proposed here seeks to characterize the structure and organization of carboxysomes, a model BMC responsible
for carbon fixation in cyanobacteria. High-resolution cryo-electron tomography and sub-tomogram averaging will
be used to determine cargo organization and shell ultrastructure in vitro and in vivo, preserving and
characterizing the conserved heterogeneity of the structures. In addition to providing new insights into BMC
biology and its conserved complexity, this research will also generate new analysis methods that can be applied
to many complicated BMC and viral systems.

## Key facts

- **NIH application ID:** 9908429
- **Project number:** 1F32GM135994-01
- **Recipient organization:** CALIFORNIA INSTITUTE OF TECHNOLOGY
- **Principal Investigator:** Lauren Ann Metskas
- **Activity code:** F32 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2020
- **Award amount:** $67,446
- **Award type:** 1
- **Project period:** 2020-02-01 → 2022-01-31

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/9908429

## Citation

> US National Institutes of Health, RePORTER application 9908429, Bacterial Microcompartment Cargo Packing and Ultrastructure: High-Resolution Studies of Native Alpha-Carboxysomes (1F32GM135994-01). Retrieved via AI Analytics 2026-05-23 from https://api.ai-analytics.org/grant/nih/9908429. Licensed CC0.

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